History of Hispanic and Latino Americans in the United States
In 1821, Mexico gained independence from Spain, annexing the southwest of the present United States, including Arizona. As missions began to wither, Mexico began auctioning off more land, causing the Pimería Alta and the Apachería to shrink as territory expanded. In the meantime, American mountain men began to enter the region, looking to trap beavers for their pelts. In 1836, Texas declared independence from Mexico and claimed much of the territory in the northern lands of Mexico. When the United States annexed Texas in 1846 over the strong objections of the Mexican government, U.S. troops moved into disputed territory. The hostilities erupted in the Mexican–American War (1846–1848). The U.S. occupied Mexico City and forced the newly founded Mexican Republic to give up its northern half, including the later Arizona.
Military history of Mexico
The war for independence lasted eleven years until the troops of the liberating army entered Mexico City in 1821. Thus although independence from Spain was first proclaimed in 1810, it was not formalized until 1821, under the Treaty of Córdoba, which was signed on September 16 in Córdoba, Veracruz, by the Spanish viceroy Juan de O'Donojú and Agustín de Iturbide, ratifying the Plan de Iguala.