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
Declaration of Independence of the Mexican Empire of the Nation in Mexico City. The document is wide and high. On September 27, 1821, eleven years and eleven days after the Grito de Dolores, the Army of the Three Guarantees headed by Agustín de Iturbide entered Mexico City, concluding the Mexican War of Independence. On September 28, Iturbide installed the Provisional Governing Board, comprising 38 people. The board was chaired by Antonio Pérez Martínez y Robles, and Juan José Espinosa de los Monteros was secretary. The board immediately elected the five members of the Regency of the Empire. On October 13 of the same year, Ramón Gutiérrez del