On Saturday, February 24, 1821, halfway between Mexico City and Acapulco, General Agustin de Iturbide published the Plan of Iguala and effectively established Mexico’s independence from Spain and set the stage for American conquest of New Mexico, California, and the land in between.
The plan of Iguala maintained the Catholic Church as the official religion of Mexico, created an independent limited monarchy, and established equal rights for Spaniards and creoles. The new government also reversed the Spanish policy which forbade foreign merchants to enter New Mexico, thus opening the door for William Becknell and his mule train of goods as well as the many trappers and traders who would follow him down the Santa Fe Trail.
However, the new relationship with the United States was fraught with complications. Within a few years, Mexican officials realized that the Americans were taking every opportunity to keep from paying customs duties on the goods they brought into and the furs they took out of nuevomexico. Although officials tried various measures to control the Americans, nothing was really effective. The American trappers and traders continued to be a thorn in the side of the Mexican government. In fact, it could be argued that the Americans that the Mexicans allowed in after 1821 would turn out to be a major factor in the lack of resistance to the American invasion in 1846, 25 years later.
Sources: Paul Horgan, Great River, The Rio Grande in North American History, Wesleyan Univeristy Press, Middletown, CT, 1984; : Ralph E. Twitchell, The Leading Facts of New Mexico History, Vol. II, The Torch Press, Cedar Rapids, 1912; David J. Weber, The Taos Trappers, David J. Weber, U of Oklahoma Press, Norman, OK, 1970.