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.
Treaty of Córdoba
On September 27, 1821, the Army of the Three Guarantees entered triumphantly into Mexico City and on the following day, the Declaration of Independence of the Mexican Empire was widely known. The Spanish Cortes refused to accept the validity of the Plan of Iguala or the Treaty of Córdoba. Spain did not recognize Mexico's independence until December 1836. Therefore, the Mexican Congress elected a Mexican monarch the following year. Iturbide was proclaimed emperor of Mexico on May 18, 1822. The monarchy lasted three years, and after the republican revolution of Casa Mata, the Congress no longer considered the Plan of Iguala or Treaty of Córdoba in effect.