Mapa de los Estados Unidos de Mejico, John Disturnell, 1847

The Mexican Republic

Mexico became a republic in 1821, after a war for independence from Spain. In the 1840s, the new nation was still struggling to resolve the political divisions between centralists and federalists, and between liberals and conservatives. The people and their leaders debated the roles that Indians, the Catholic Church, and the military should play in public life. These tensions caused many changes of government — Mexico had thirty-four governments between 1821 and 1848.

Few Mexicans populated the nation’s northern frontier, where trade and communication with the rest of the country remained very difficult.