Mexican Cession Mexican Cession, with considerable local autonomy punctuated by several revolts and few troops sent from central Mexico, in the period from 1821–22 after independence from Spain up through 1846 when U.S. military forces seized control of California and New Mexico on the outbreak of the Mexican–American War. The northern boundary of the 42nd parallel north was set by the Adams–Onís Treaty signed by the United States and Spain in 1821 and ratified by Mexico in 1831. The eastern boundary of the Mexican Cession was the Texas claim at the Rio Grande and extending north from the headwaters of the Jojo
Antonio López de Santa Anna enough to send him to school. In June 1810, the 16-year-old Santa Anna joined the Fijo de Veracruz infantry regiment as a cadet against the wishes of his parents, who wanted him to pursue a career in commerce. In September 1810, secular cleric Miguel Hidalgo y Costilla rebelled against Spanish rule, sparking a spontaneous mass movement in Mexico's rich agricultural area, the Bajío. The Mexican War of Independence was to last until 1821, and Santa Anna, like most creole military men, fought for the crown against the mixed-raced insurgents for independence. Santa Anna's commanding officer was José Joaquín de Arredondo,