Spanish attempts to reconquer Mexico
Mexican independence was officially achieved on September 27, 1821, under the Treaty of Córdoba. Spain did not recognize the treaties, arguing that the viceroy Juan O'Donojú had no authority to recognize the independence of any overseas province. This situation was dangerous to the newly acquired independent status of the nation, which had not yet been recognized by any of the European powers that could support it, and the threat of Spanish reconquest was a constant worry to the leaders of the nascent regime. On May 13, 1822 decrees were issued by the government to imprison anyone who conspired against Mexico's independence.
San Luis Obispo, California
When the Mexican War of Independence from Spain broke out in 1810, all California missions had to become virtually self-sufficient, receiving few funds or supplies from Spanish sources. Beginning soon after Mexico won her independence from Spain in 1821, anti-Spanish feelings led to calls for expulsion of the Spanish Franciscans and secularization of the missions. Because the fledgling Mexican government had many more important problems to deal with than far-off California, actual secularization didn't happen until the mid-1830s.