Indigenous peoples of Mexico
When Mexico gained independence in 1821, the casta system was eliminated as a legal structure, but racial divides remained. 
White Mexican argued about what the solution was to the "Indian Problem", that is indigenous who continued to live in communities and were not integrated politically or socially as citizens of the new republic. The Mexican constitution of 1824 has several articles pertaining to indigenous peoples. The second article of the constitution of Mexico recognizes and enforces the right of indigenous peoples and communities to self-determination and therefore their autonomy to:
List of ambassadors of the United States to Mexico
Mexico achieved independence from Spain in 1821; so the first three men on this list were sent by President Madison during the Mexican War of Independence (1810–1821). William Shaler participated in the 1812–13 Gutiérrez–Magee Expedition, which was a private military campaign to overthrow the Royalists and resulted in the roadside murder of two provincial governors and about a dozen other officials.