Bolivia, republic in central South America, bounded on the north and east by Brazil, on the southeast by Paraguay, on the south by Argentina, and on the west by Chile and Peru. Bolivia and Paraguay are the only South American countries without direct access to the sea. The maximum length of Bolivia from north to south is about 1,530 km (about 950 mi); its maximum breadth is about 1,450 km (about 900 mi). Its area is 1,098,581 sq km (424,164 sq mi), making it fifth in size (after Brazil, Argentina, Peru, and Colombia) of South American countries. The constitutional capital of Bolivia is Sucre; La Paz is the largest city and administrative capital.

Nicknamed the Rooftop of the World because of its high elevation in the Andes Mountains, Bolivia has a landscape of snow-topped mountain peaks and broad, windswept plateaus 4 km (2.5 m) above sea level. To the east of the mountains, vast grassy plains give way to lowland tropical rain forests. Most of the people live in the Andes Mountains, which occupy a third of the country. Since the 1950s, however, the sparsely settled, eastern lowland plains have gradually become more populous because of significant discoveries of oil and gas.

The great majority of the people in Bolivia are Native American or part Native American, and ancient traditions are still practiced, particularly in rural areas. From the 16th to the early 19th century, Bolivia was a colony of Spain. In 1952 Bolivia underwent a political revolution that brought about major changes throughout the country. The leaders of that revolution introduced programs designed to provide greater political, economic, and social opportunities for Native Americans. The government extended the vote to Native Americans, enrolled remote villages in national organizations, and extended commercial networks. The government also redistributed land, breaking up the large estates established during colonial times and giving small plots of land to Native American farmers.

The principal physical feature of Bolivia is the Andes mountain range, which extends generally north to south across the western part of the country. The Andes form two ranges in Bolivia, the western range (Cordillera Occidental), which runs along the Chilean border, and the eastern range (Cordillera Oriental), the main range, which crosses the west central part of Bolivia. The Cordillera Oriental contains some of the highest Andean peaks, notably Ancohuma (6,388 m/20,958 ft), Illampu (6,360 m/20,867 ft), and Illimani (6,462 m/21,201 ft).

Bolivia is divided into three distinct regions: the Altiplano, or plateau region; the Yungas, a series of forested and well-watered valleys embracing the eastern mountain slopes and valleys; and the llanos, or the Amazon-Chaco lowlands. The Altiplano is about 800 km (about 500 mi) long and about 130 km (about 80 mi) wide and lies between the Cordillera Occidental and the Cordillera Oriental. In the northern part of the Altiplano, where the bulk of the population and industry of Bolivia is found, is Lake Titicaca, the highest large, navigable lake in the world. The southern part of the plateau is arid.

Stretching east and northeast from the mountains are the great Amazonian plains (llanos) containing large grassy tracts and, along the rivers, dense tropical forests. Much of this region becomes swampland during the wet season (December through February); large areas, however, lie above the flood line and are rich grazing lands. In the southeast, separated from the Amazonian plains by the Chiquitos highlands (about 1,070 m/about 3,500 ft), are the dry, semitropical plains of the Chaco (see Gran Chaco).

In the northern and northeastern valleys and plains, the drainage system consists of the Beni River and its main affluent, the Madre de Diós River; the Guaporé River, which forms part of the boundary with Brazil; and the Mamoré River. These rivers flow north to join the Amazon River. The Pilcomayo River, the chief river of southeastern Bolivia, flows through the Chaco to feed the Paraguay River, eventually draining into the Río de la Plata, a large estuary that empties into the Atlantic Ocean between Argentina and Uruguay. The Desaguadero River, outlet for Lake Titicaca, feeds Lake Poopó to the southeast.

Although situated entirely within the tropics, Bolivia has, as a result of its varied elevation, a wide range of climate. In the higher regions the climate is cold and dry. In the lower-lying regions the climate is warmer. The mean annual temperatures range from 8�C (47�F) in the Altiplano to 26�C (79�F) in the eastern lowlands.

Deposits of metallic ores are large and varied. Mineral resources include tin, lead, silver, copper, antimony, zinc, sulfur, bismuth, gold, and tungsten. Salt, petroleum, and natural gas are also found. The soil of certain regions, notably the valleys east of Santa Cruz (the Valle), is extremely fertile. The output of hydroelectric plants in 1999 amounted to 1.5 billion kilowatt-hours, 56 percent of Bolivia�s total.

Because of the wide variations in elevation, plant and animal species of nearly every climatic zone are found in Bolivia. A coarse grass, called ichu, grows on the largely barren high plateau in the west. Para rubber trees, more than 2,000 species of hardwood trees, and vanilla, sarsaparilla, and saffron plants are common in the tropical forests of the east. The llama, found chiefly on the Altiplano, is an efficient beast of burden. Alpaca and vicuña also inhabit the plateau, and monkeys, pumas, jaguars, armadillos, and a variety of reptiles, birds, and insects are found predominantly in the tropical Amazon Basin.

The population of Bolivia (2001 estimate) is 8,300,463, giving the country a population density of 8 persons per sq km (20 per sq mi), one of the lowest in South America. Roughly 55 percent of all the people are Native American, and about 30 percent are mestizo (of mixed Native American and European ancestry). The remaining inhabitants are white, mainly of Spanish descent. Some 36 percent of the people live in rural areas.

The official languages of Bolivia are Spanish and two Native South American languages, Quechua and Aymara; of those the Native American languages are more commonly spoken. Roman Catholicism is the religion of the great majority of the population.

The Native Americans are divided into the two major native language groups, the Aymara and the Quechua. Of the groups that presently live in Bolivia, the Aymara have probably been there the longest. They had a well-developed civilization along the shores of Lake Titicaca for many centuries before the Quechua-speaking Incas conquered them. Native American language, religion, and customs prevail in rural areas, and the Native American influence remains strong in the poorer districts of even major cities.

In past centuries the indigenous communities resisted European influences, a response to the European conquest of the region in the early 1500s. European settlers established a rigid class system in which an upper class of European colonists ruled over a lower class of Native Americans.

The Bolivian upper classes speak Spanish and trace their ancestry to the early Spanish colonists. However, since the settlers and Native Americans intermixed from the very beginning of the conquest, few of the old aristocratic families can claim pure European ancestry. Until the 1950s these aristocratic families, plus a few recent immigrants from other South American countries and Europe, had a monopoly on wealth, education, and political power. They owned almost all the land and controlled most large businesses and some of the mining industry. Even the country�s educational system was geared to training this elite. Since the revolution of 1952, however, Bolivian society has become more open and allows for more social mobility.

The republic is divided into nine major political divisions, called departments: Santa Cruz, El Beni, Tarija, Potosí, La Paz, Chuquisaca, Pando, Cochabamba, and Oruro. La Paz is Bolivia�s largest city and is also its administrative capital (population, 1998 estimate, 940,281). Other important cities are Santa Cruz (935,361), a major trade center; Cochabamba (565,395), in a fertile farming region; Oruro (223,553), in the mining district; Sucre (178,426), the country�s constitutional capital; and Potosí (140,642), also in a mineral-producing region.

Primary education is nominally free and compulsory for children between the ages of 6 and 14. However, the public schools, although increasing in number, do not meet the needs of Bolivia. The country�s literacy rate is 96 percent.

In 1996 almost all children were enrolled in primary schools. Only 40 percent of secondary school-aged children attended school. Enrollment in institutions of higher education was 24 percent.

Bolivia has ten universities: in Sucre, La Paz (two), Cochabamba, Llallagua, Oruro, Potosí, Santa Cruz, Tarija, and Trinidad. San Francisco Xavier University (1624), in Sucre, is one of the oldest in the Americas. The University of San Andrés (1830), in La Paz, is the largest university in Bolivia, with a student enrollment of about 37,000.

In dress, language, architecture, and lifestyle, the large Native American population follows the ways of its ancestors with a mixture of modified Spanish traditions. Clothing is colorful and suited to life in high altitudes. For example, many Bolivian women wear brightly colored Native American clothing and stovepipe or derby hats. Holidays and religious festivals are celebrated by dancing and festivities. The Spanish-speaking population, which is largely European in ancestry, has adopted some of the Native American customs but generally follows Western traditions.

Indigenous and Spanish colonial influences have fused to produce the culture of modern Bolivia. Native American traditions are strong in painting, literature, music, dancing, and folklore. Many contemporary painters have been inspired by indigenous art. Spanish influence prevails in music and folk dances of the valleys, while the austere and plaintive native tradition predominates in the highlands. Pre-Columbian and Spanish-colonial instruments are widely used, among them the gigantic panpipes, called sicus or bajones; the native flute, or quena; and the armadillo-shell guitar, or charango. See Latin American Literature; Latin American Music.

La Paz is home to the Archaeological Society; the National Museum; the National Academy of Fine Arts; the Tiahuanaco Institute of Anthropology, Ethnology, and Prehistory; and the Atheneum. Important libraries are the National Library and Archives in Sucre, the Santa Cruz Municipal Library in La Paz, and the libraries of the University of San Andrés in La Paz and the University of San Francisco Xavier in Sucre.

Since early colonial times, mining for precious minerals and metal ores has played an important role in Bolivia�s economy. Although many of the largest mining operations were nationalized during the 1950s, successive Bolivian governments have encouraged private industrial development and actively sought foreign investment capital. Budget figures for 1998 showed revenues of $1.5 billion and expenditures of $1.9 billion. The state airline, Lloyd Aéreo Boliviano, was sold to private interests in 1993. In 1995 Bolivia began implementing a unique privatization program in which additional state-owned companies would not be sold outright; instead, half of the company�s shares and management control would be awarded to the highest private bidder. The remaining shares would be divided among Bolivia�s adult population and held in retirement accounts that would form a new private pension system. Despite these efforts to deflect charges that Bolivia was �selling out� its resources to foreigners, the privatization efforts drew sustained criticism and prompted serious labor strife. In June 1995 Bolivia sold a controlling interest in the state electricity company to three U.S. firms. In 1996 the state railroad was privatized and the state petroleum company was put up for sale. Bolivia�s estimated gross domestic product (GDP) in 1999 was $8.3 billion.

Agriculture is extremely important to the Bolivian economy, employing 2 percent of the labor force. Farming, fishing, and forestry accounted for 18 percent of the gross domestic product (GDP) in 1999. Bolivia�s agriculture suffers from antiquated farming methods, uneven population distribution, and inadequate transportation. Although now self-sufficient in the production of sugar, rice, and meat, Bolivia must still import certain foodstuffs. The chief Bolivian crops are soybeans, sugar, chestnuts, potatoes, cassava, bananas, maize, rice, plantains, and citrus fruits. Fishing is a relatively unimportant industry in landlocked Bolivia. The lack of transportation facilities has prevented large-scale exploitation of wealth in the Bolivian forests, which cover 49 percent of the country�s area, mostly in the east.

Mining, a major industry in Bolivia, was hampered in the late 1980s by weak prices on world markets. Bolivia has long been one of the world�s leading producers of tin. In 1952 its three major tin-mining operations were nationalized under the Corporación Minera de Bolivia (COMIBOL). Most of the tin mines are located in the vicinity of Oruro; the output of tin concentrates in 1999 was 11,300 metric tons. Also mined are gold, zinc, lead, antimony, tungsten, and silver. Petroleum and natural gas production increased in importance in the 1960s and early 1970s; by the early 1990s Bolivia was self-sufficient in petroleum and was exporting significant amounts of natural gas to Argentina.

Manufacturing enterprises are on a small scale. The manufacture of cement and the refining of sugar and flour are Bolivia�s major industries. Smaller industries include leather working, tobacco processing, and the manufacture of chemicals, paper, furniture, glass, explosives, and matches. More than two-thirds of all manufacturing is in La Paz, which is also the center of domestic trade. In 1999 industry, which includes mining, manufacturing, and construction, accounted for 18 percent of the GDP. Industry employed 29 percent of the workers.

Although Bolivia has long been dependent on mineral exports, declining tin prices and increased petroleum and natural gas production changed the nature of the country�s economy in the 1980s. By the early 1990s, natural gas accounted for 27 percent of export earnings while tin provided just 12 percent. Zinc, silver, gold, lead, and antimony are other important mineral exports. Soybeans, wood, and sugar are also exported. Bolivia�s imports consist mainly of machinery, motor vehicles, electric equipment, and manufactured goods. In 1999 imports totaled $1.8 billion, and exports earned $1 billion.

The principal purchasers of Bolivia�s exports are the United States, the United Kingdom, Peru, Colombia, Argentina, Germany, The Netherlands, and France. Chief suppliers of imports are the United States, Brazil, Japan, Argentina, Chile, Peru, and Germany. Ties with Andean Group partners are also important to Bolivia�s trade; these partners include Colombia, Ecuador, Peru, and Venezuela. Founded in 1979, the group works toward common policies on energy, tariff reduction, industrial and agricultural development, political cooperation, improved internal and international trade, and the creation of a common market. Bolivia is also a member of the Latin American Integration Association (LAIA), an organization with many of the same goals as the Andean Group, but on a wider scale. In 1996 Bolivia joined the Southern Cone Common Market (known by its Spanish acronym, MERCOSUR), a trade group dedicated to lowering tariffs and removing other trade barriers among its member nations. MERCOSUR�which also includes Argentina, Brazil, Paraguay, and Uruguay�covered a market of more than 190 million people in 1995, making it the world�s fourth-largest free trade group.

The basic unit of currency is the boliviano, equivalent to 1 million old Bolivian pesos (5.81 bolivianos equal U.S.$1; 1999 average). The Banco Central de Bolivia is the sole bank of issue. Several state-owned development banks provide investment credits to small mining and agricultural operations. Foreign and domestic private financial institutions also operate in the country.

Bolivia has 3,698 km (2,298 mi) of railroad tracks. Railroads connect the landlocked country to ports on both the Atlantic and Pacific oceans. The principal line connects La Paz with the free port of Antofagasta, Chile. Bolivia also has free port privileges in the maritime facilities of Argentina, Brazil, and Paraguay.

About 49,400 km (about 30,696 mi) of roads exist in Bolivia; only a few are hard-surfaced, and many are passable only in the dry season. In 1996 Bolivia announced plans to build a $100 million two-lane paved highway between the highland city of La Paz and the lowland tropical communities of eastern Bolivia, the country�s most productive agricultural region. The project will transform a one-lane dirt road that dates back to Inca times and vastly improve the only direct link between the capital and the Amazonian lowlands. Light-draft water vessels can navigate about 10,000 km (about 6,000 mi) of the nation�s rivers.

In 1997 there were 675 radios and 116 television receivers in use for every 1,000 inhabitants; in 1999 there were 62 telephone mainlines per 1,000 people. Bolivia has 18 daily newspapers.

Bolivia�s labor force was 3.3 million in 1999. Nearly the entire nonfarm labor force is organized, most of it in unions belonging to the Central Obrera Boliviana (COB), the central labor federation. Peasant unions were established after the 1952 revolution.

Bolivia is a republic governed under a constitution passed in 1967 and since amended.

Executive power is vested in a president and vice president, elected by direct popular vote of married people over the age of 18 and single people over 21. A 1995 constitutional amendment extended the presidential term from four years to five. Neither the president nor the vice president can be reelected to an immediate succeeding term. The president appoints the cabinet. Among other presidential powers is the right to rule by decree.

The Bolivian congress is bicameral, composed of a senate of 27 members (3 from each department) and a chamber of deputies of 130 members. All are elected for four-year terms.

The principal political parties are the Movement of the Revolutionary Left (MIR), the Nationalist Revolutionary Movement (MNR), and Nationalist Democratic Action Party (ADN).

Bolivia is divided into nine departments administered by prefects appointed by the president. Each department is divided into provinces, administered by subprefects appointed by the president. Important cities and towns have popularly elected councils.

Justice is administered by the Supreme Court, which is composed of 12 members, elected by the congress to ten-year terms, and by district and local courts. Military training is universal and compulsory, but in practice only a small percentage of those registered for service are drafted. In 1999 the combined strength of the armed forces was 32,500.

Health conditions are poor in Bolivia. In 1998 the country had 1 physician for every 2,688 inhabitants. The infant mortality rate is among the highest in South America; malaria, dysentery, and tuberculosis are common, and there was a serious outbreak of yellow fever in the late 1980s. Medical services and hospitals are particularly inadequate in rural areas. Bolivia has a comprehensive social insurance plan, but it covers less than half the working population.

Civilized cultures have lived in the area of modern-day Bolivia for more than 1,000 years. The ancient Tiahuanaco civilization developed along the shores of Lake Titicaca around ad 600 and left impressive stone monuments. However, little is known about the origins of this group. In about 1300 the Quechua-speaking Incas, who came across the lake from present-day Peru, overran Tiahuanaco. When the Spaniards arrived in South America in the early 16th century, the Inca Empire, of which Bolivia was a part, was divided by civil strife, with two rival nobles claiming the throne. The Spanish took advantage of this strife to conquer the empire.

The territory of Bolivia was conquered in 1538 by Spanish conquistador Hernando Pizarro, younger brother of Spanish explorer Francisco Pizarro. The elder Pizarro had subdued Peru, which was the heart of the Inca Empire. Within the next 40 years, Spanish settlements were formed at Chuquisaca (present-day Sucre), Potosí, La Paz, and Cochabamba.

The region was first called the province of Charcas and later Alto Perú (Upper Peru). It was governed by an audiencia (a judicial body with executive powers) under the viceroyalty of Peru. In 1776 Spain transferred Bolivia to the newly created viceroyalty of La Plata, which administered Bolivia from what is now Buenos Aires, Argentina.

Throughout the three centuries of the colonial period, Bolivia was important to Spain because of its rich silver mines located at Potosí, which until the 18th century was the largest city in colonial America. Bolivia�s silver mines produced several hundred million dollars worth of silver, extracted from the mines by Native Americans. They worked under the dreaded mita, or obligatory service system, which required Native Americans to work a specified number of hours in the mines each year. This system led to many uprisings, the most formidable of which was an insurrection in 1780 under the leadership of Tupac Amarú, who claimed to be descended from Inca royalty.

For centuries the production of minerals for export was Bolivia�s most important economic activity, and other areas of the economy were neglected. From early colonial times, Bolivia imported food and most manufactured goods to supplement the meager output of its farms and rudimentary local industries. Mining began to decline in the 18th century, and by the end of the century the industry had stagnated.

Bolivia was one of the first countries in the Spanish Empire to attempt a break from Spain, but it was one of the last to succeed. The Spanish suppressed the first critical rebellion at Chuquisaca in May 1809. Fifteen years later a revolutionary army under General Antonio José de Sucre liberated Bolivia after defeating Spanish forces at the Battle of Ayacucho in Peru on December 9, 1824. Bolivia declared its independence from Spain on August 6, 1825, and took the name Bolivia in honor of South American independence leader Simón Bolívar. In 1826 a congress at Chuquisaca adopted a constitution drafted by Bolívar. It vested supreme authority in a president, who was chosen for a life term.

From the beginning of its national existence, Bolivia was plunged into a state of nearly chronic revolution and civil war. The first president, General Antonio José de Sucre, was expelled from the country after holding office for only two years. During the next half century, interludes of political tranquility were brief and infrequent. Between 1836 and 1839 Bolivia was in a confederation with Peru, but a Chilean invasion brought an effective end to it, increasing the turbulence. Short wars and disputes with both Peru and Chile followed.

Bolivia became involved in a number of border disputes between the mid-19th and mid-20th centuries. One of the earliest disputes involved the ill-defined borders with Peru and Chile along the Pacific Coast in the region of the Atacama Desert. The disputed area became the center of controversy following the discovery of rich deposits of nitrate, a mineral used in fertilizer production. In treaties made in 1866 and 1874, Bolivia and Chile adopted the 24th parallel of south latitude as the boundary line in that region. In addition, the treaty granted to Chile various customs and mining concessions in Bolivia�s portion of the Atacama. Disputes arose between the two countries over the latter provisions, and in 1879 Chile seized the Bolivian port of Antofagasta. In the resulting struggle, called the War of the Pacific, Chile defeated Bolivia and its ally Peru. Bolivia lost its one seacoast possession, becoming a landlocked country. A treaty ratified in December 1904 recognized the perpetual dominion of Chile over the disputed territory but granted Bolivia free access to the sea. A dispute with Brazil concerning the possession of the Acre region was settled in 1903. The agreement ceded about 180,000 sq km (about 70,000 sq mi) to Brazil in return for a money indemnity and small territorial compensations elsewhere.

In the first two decades of the 20th century, Bolivia enjoyed the longest period of peace and progress in its history. The exploitation of tin resources, begun in 1899, made Bolivia one of the world�s major tin suppliers. Several Bolivians, later known as the tin barons, made large fortunes from tin mining. British and U.S. investors became interested in the industry in its early stages, and they invested a considerable amount of capital.

This boom in the tin-mining industry coincided with Liberal Party administrations. The government helped the industry by only lightly taxing the new mining interests and by expanding the country�s existing rail system. The Republican Union Party overthrew the Liberal Party in 1920 and remained in power for the following 15 years. Under the new administration, relatively little changed in economic policy. During this period the first important manufacturing industries were established.

The Bolivian government subsequently became involved in boundary disputes with Argentina, Peru, and Paraguay. Bolivia reached a peaceful solution to the dispute with Argentina in 1925. In the 1930s Peru and Bolivia appointed a joint commission that decided the border disputes over the peninsula of Copacabana.

The Paraguay-Bolivia boundary dispute arose over the Chaco Boreal, a low region to the north of the Pilcomayo River, to the west of the Paraguay River, and extending to the undisputed boundary of Bolivia. Both Bolivia and Paraguay claimed the entire territory, which was believed to contain large reserves of petroleum. In July 1932 an undeclared war broke out (see Chaco War). As in every other international conflict in which the country had been involved, Bolivia lost this bloody struggle. A peace treaty ended the conflict in July 1938.

The period after 1930 was marked by internal strife. In that year, President Hernando Siles, who had governed for two years without convening the national legislature, was overthrown in a revolution. Daniel Salamanca was elected president in 1931, but he was overthrown in 1934 by a coup under Vice President Tejada Sorzano.

The poor performance of Bolivia�s armed forces in the Chaco War gave impetus to dissident political currents, particularly among young intellectuals who had made up much of the junior officer class during the war. Their social consciousness was stimulated by the ineffectiveness and greed of professional military officers and politicians, and by the suffering of Native American soldiers unaccustomed to the world outside their mountain homes. Old political groups favoring the tin barons were discredited as many people began to realize that a combination of native and foreign exploiters was draining the country�s resources.

Widespread discontent was first expressed in the revolution of May 1936, led by Colonel David Toro, who proclaimed Bolivia a socialist republic. Toro seized the property of U.S. petroleum giant Standard Oil Company and encouraged organized labor in Bolivia. Toro was largely successful in improving the desperate conditions caused by the Chaco War and the worldwide economic depression of the 1930s. He made enemies in influential quarters, however, and in 1937 a group led by Lieutenant Colonel Germán Busch ousted Toro.

In 1938, during Busch�s second term as president, a new constitution was adopted. His regime enacted the country�s first labor code, abolished the system of tenant services to landlords, and set up controls over the mining industry. Busch abolished the new constitution in April 1939, however, and set up a totalitarian state. Four months later he was found dead of a bullet wound, an alleged suicide.

General Carlos Quintanilla then assumed the presidency. He restored the 1938 constitution and stated that the army would exercise control until new elections could be held. In 1940 General Enrique Peñaranda was elected president, and on April 7, 1943, during World War II, he declared war against the Axis powers.

Popular discontent continued, however. During the 1940s several leftist-oriented political parties were organized. The most important of these was the Nationalist Revolutionary Movement (Movimiento Nacionalista Revolucionario, or MNR), founded by young nationalist intellectuals and headed by Víctor Paz Estenssoro, an economist and one-time close adviser to Colonel Busch. The MNR opposed the power of the big mining companies and advocated freeing the Native American people from exploitation. The party became popular among miners in December 1942, after it disclosed before congress the government�s responsibility for a massacre at the Catavi mine in which soldiers killed strikers, women, and children.

In December 1943 the MNR led a coup that ousted Peñaranda. The new government, headed by Lieutenant Colonel Gualberto Villarroél, encouraged unionization of tin mines and tried to improve Native American living conditions. These efforts brought the government into conflict with the tin barons. The barons used their influence to create discord. The tin market collapsed after World War II ended in 1945, and the discord culminated in a bloody uprising in La Paz in July 1946 and the death of Villarroél. For the next six years the government remained in the hands of the conservative Socialist Republican Union Party. Enrique Hertzog was elected president in 1947; Mamerto Urriolagoitia succeeded him in 1949.

After Villarroél was killed in 1946, Víctor Paz Estenssoro fled to Buenos Aries, Argentina. In May 1951 Paz Estenssoro won nearly half the presidential election vote while in exile. Because no candidate had a clear majority of the vote, election of a president from among the three leading candidates fell to the congress. In order to prevent the election of Paz Estenssoro, the incumbent president, Urriolagoitia, placed the government under the control of a military junta and resigned. General Hugo Ballivián was appointed president.

On April 9, 1952, a revolution by the MNR and the miners put Paz Estenssoro in the presidency, and the MNR began its program of profound social, economic, and political changes. It pledged to make Native Americans full-fledged members of the national community, to free the country from control of the largely foreign-owned mining companies, to develop the economy, and to bring about real political democracy.

The revolutionary regime acted quickly. In August 1952 it extended the vote to all adults. A year later, through its land reform law, it broke up the estates of the large landlords and transferred ownership of the small plots to Native American farmers. It began extensive projects for education and founded medical clinics in the countryside and farm cooperatives among the peasants. The new government expropriated the holdings of the major tin-mining companies and placed them in the hands of a new state firm. The government financed and directed the construction of roads, hydroelectric projects, and industrial plants. It also opened new areas for settlement, with particular attention given to the undeveloped eastern part of Bolivia.

The MNR�s development program faced major foreign and domestic obstacles. The country�s inflation was soaring because of declining income from mining (a result of low tin prices in the world market), ambitious economic development programs, corruption, and the departure of much foreign and native capital from the country. The administration of the second MNR president, Hernán Siles Zuazo, began in 1956 and took major steps to counteract inflation. In conjunction with the International Monetary Fund (IMF) and the United States, the regime launched a stabilization program that limited wage increases, abolished most price controls, and reduced government spending. These measures did not end the economic crisis, and Paz Estenssoro was confronted with these problems when he returned to the presidency in 1960. A rise in agricultural and mineral production led to a partial recovery, however.

During its years in power, the MNR provided Bolivia with the most stable and open government in the country�s history. The press was free to criticize the government and did so energetically. Government changes in 1956 and 1960 were the results of elections, although there were frequent crises and many coup d�état attempts to oust the MNR.

By the mid-1960s the MNR occupied the center in Bolivian politics. The MNR made economic concessions to the IMF to encourage international investments. These concessions cost the party the support of many of the miners who formed the backbone of the independent militia that had supported the revolution. Many miners withdrew from the MNR to form the Revolutionary Party of the Nationalist Left (Partido Revolucionario de la Izquierda Nacionalista, or PRIN). Opposition to the Paz Estenssoro government increased on the left and the right.

The Bolivian military, weakened since the revolution, reasserted its place in Bolivian politics and overthrew Paz Estenssoro in 1965. A military junta used force to suppress the opposition of the miners and the mine unions. General René Barrientos Ortuno, a member of the junta, was elected president in July 1966. Although he retained most of the revolution�s programs, in the ensuing two years, the military government reopened tin-mining operations to private and foreign investment.

Barrientos, who was elected to the presidency as a civilian, relied heavily on armed force to put down Communist-led guerrilla movements concentrated in the mountainous mining regions. The Bolivian army reportedly smashed the rebel forces in October 1967 in a pitched battle near the village of Vallegrande. Che Guevara, aide to Cuban premier Fidel Castro, was captured in that encounter and was executed shortly afterward. Barrientos died in a helicopter crash in April 1969, and a series of short-lived governments followed, most headed by military leaders.

In August 1971 a coup supported by the right and the center brought Colonel Hugo Banzer Suárez to power. With business support, Banzer ruled as president for seven years. His regime attracted foreign investment, and in the mid-1970s it also benefited from increased earnings from tin and oil. However, it continued to face opposition from workers and students. In 1972 Banzer invoked martial law. He also silenced many political opponents and suppressed protests by peasants. After an abortive coup in 1974, Banzer suspended all political parties, trade unions, and student groups.

Banzer stepped down in 1978 pending restoration of civilian government, but elections in 1979 and 1980 were followed by renewed military intervention. By 1982 the country�s earnings from tin production had declined, and foreign debt continued to rise. During this time, the illegal export of cocaine from Bolivia began to thrive. The United States pressured Bolivia to take decisive steps against the drug traffic.

In July 1980 General Luís García Meza seized power, suspended the constitution, and instituted a repressive regime. Many politicians, labor leaders, and military men who opposed García Meza were arrested and killed, and many more fled abroad. The government closed the universities. Cocaine�already the major source of export and peasant incomes�became a major source of income among government officials. Drug traffickers paid bribes to judges, politicians, and military officers in exchange for protection from prosecution and the ability to trade drugs without interference. The army ousted García Meza in August 1981, and moderate army leadership held power until elections were held in October 1982.

Former president Hernán Siles Zuazo was installed as president; he faced several cabinet crises and could not resolve economic problems caused by Bolivia�s huge foreign debt. Presidential elections in 1985 returned Paz Estenssoro to the presidency. With backing from the IMF, Paz Estenssoro immediately imposed a drastic deflationary program. A new currency unit, the boliviano, was introduced to replace the near-worthless peso at the rate of 1 to 1 million. Paz Estenssoro�s administration slashed government employment and subsidies and closed most of the tin mines, which were considered unprofitable. The resulting strikes and demonstrations were repressed. Unemployment and poverty soared, but the rate of inflation was reduced to less than 20 percent per year. By 1988 a modest economic recovery had begun. The government attempted to cut down coca production and the sale of cocaine. It was aided by a contingent of U.S. troops from July to November 1986, but the efforts were only partially successful and were very unpopular.

Jaime Paz Zamora, who finished third in the popular election of May 1989, became president of Bolivia in August after winning a congressional runoff. Mining entrepreneur Gonzalo Sánchez de Lozada won the next presidential election, held in June 1993. Sánchez de Lozada�s vice president, Víctor Hugo Cárdenas, was the first Native American to hold such a high office in Bolivia. Sánchez de Lozada worked to implement a number of reforms intended to give more economic and political power to Bolivia�s Native American majority. He oversaw a redistribution of the federal budget that increased money for roads, schools, and water projects in largely rural areas. The government also legalized native organizations and the practice of folk medicine, both of which had previously been outlawed. In addition, the government allowed bilingual education in Spanish and Native American dialects in schools that previously had been prohibited from teaching any language other than Spanish.

As the government continued to work to promote a free market in Bolivia, it moved toward privatizing state oil holdings in 1995 and 1996. Bolivian labor activists responded by staging a series of strikes and protests calling for higher wages and the end of plans to privatize the oil industry. In April 1995 thousands of union workers and state employees held more than three weeks of civil disturbances. Their actions prompted the government to arrest more than 300 labor leaders and to suspend constitutional rights so that the government could hold people in prison without a trial. When the protest campaign resumed in 1996, the government deployed soldiers and police to protect refineries and pipeline facilities.

Former dictator and retired general Hugo Banzer Suárez, a candidate of the right-wing Nationalist Democratic Action Party (ADN), finished first in Bolivia�s June 1997 presidential election, but he did not capture enough votes to win the presidency outright. In August members of Bolivia�s congress elected Banzer president in a runoff between him and second-place finisher Senator Juan Carlos Durán of the MNR. Banzer pledged to continue the previous government�s free market reforms and its efforts to combat the illegal drug trade. In late 1997 the Bolivian government launched the so-called Dignity Plan, an effort funded largely by the United States to eradicate coca production in Bolivia by 2002.

Coca producers rejected the government�s aggressive new anticoca policy, and coca farmer unions vowed to defend their crops. Sporadic clashes with Bolivian soldiers ensued, and in September 2000 angry farmers blockaded many of Bolivia�s key roads. The blockades caused widespread food shortages and at least ten deaths, and cost the Bolivian economy more than $100 million.