A republic in North America, situated between the United States and Central America, bordering on the Caribbean Sea and the Pacific Ocean. Mexico was the center of a number of Indian cultures dating from c. 800 B.C. By the 15th century, the central portion of the country was ruled by the Aztec Empire, which was conquered by the Spanish in 1519-21. Mexico, as the viceroyalty of New Spain, was the center of Spain's North American Empire for 300 years. The Mexican revolution against Spain began in 1810 and finally succeeded in 1821. The Mexican Empire of 1822-23 included Central America, but this area soon became independent. The republican government that succeeded the empire was marked by instability and strife. The weakened condition of the country cost it Texas (1836) and the large northern area that now comprises the southwestern United States (1848). An additional area in the north was sold to the United States in 1853. During 1861-67, Mexico was torn by a civil war between the aristocracy, supported by France, and the lower classes, led by Benito Juarez.
The French were finally expelled from Mexico, and Juarez came to power. During most of the period between 1877 and 1911, the country was ruled by the dictator Porfirio Diaz, who restored stability and secured foreign investment. After Diaz's death, Mexico entered a period of civil war, which lasted from 1913-20. During this period, the United States intervened in Veracruz (1914) and sent a punitive expedition into northern Mexico (1916-17). Since 1929, Mexico has been ruled by the Institutional Revolutionary Party. The PRI is a broad-based political confederation, encompassing a wide political spectrum. Mexico has rich natural resources, including what may be the world's largest petroleum reserves, but its rugged topography and arid climate have been major obstacles to economic development. Considerable economic and social progress has been made since 1940. The Mexican economy has improved greatly, although setbacks in the 1980s have left continuing employment and banking problems. In the 1990s, the PRI (Institutional Revolutionary Party), which has controlled the country since 1920, saw gains from hitherto powerless opposition parties. Nevertheless, the PRI elite continues to maintain a tight hold on political power in Mexico.