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.
Mexico
In 1813 the Congress of Chilpancingo was convened and, on November 6, signed the "Solemn Act of the Declaration of Independence of Northern America". Morelos was captured and executed on December 22, 1815.
In subsequent years, the insurgency was near collapse, but in 1820 Viceroy Juan Ruiz de Apodaca sent an army under the criollo general Agustín de Iturbide against the troops of Vicente Guerrero. Instead, Iturbide approached Guerrero to join forces, and on August 24, 1821 representatives of the Spanish Crown and Iturbide signed the "Treaty of Córdoba" and the "Declaration of Independence of the Mexican Empire", which recognized the independence of Mexico under the terms of the "Plan of Iguala".