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.
Spanish attempts to reconquer Mexico
The newly independent nation of Mexico was in dire straits after eleven years of fighting its War of Independence. There were no clear plans or guidelines established by the revolutionaries, and internal struggles by different factions for control of the government ensued. Mexico suffered a complete lack of funds to administer a country of over 4.5 million km², and faced the threats of emerging internal rebellions and of invasion by Spanish forces from their base in nearby Cuba.