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Administrative divisions

The boundaries and constituent units of Mexico evolved from its colonial-era origins. Central America peacefully separated from Mexico after independence in 1821. Yucatán was briefly an independent republic. Texas separated in the Texas Revolution and when it was annexed to the U.S. in 1845, it set the stage for the Mexican–American War and major territorial loss to the U.S. The sale of northern territory known in the U.S. as the Gadsden Purchase was the last loss of Mexican territory. The United Mexican States are a federation of 31 free and sovereign states, which form a union that exercises a degree of jurisdiction over Mexico City. Each state has its constitution, congress, and a judiciary, and its citizens elect by direct voting a governor for a six-year term, and representatives to their respective unicameral state congresses for three-year terms.

Mexico City is a special political division that belongs to the federation as a whole and not to a particular state. Formerly known as the Federal District, its autonomy was previously limited relative to that of the states. It dropped this designation in 2016 and is in the process of achieving greater political autonomy by becoming a federal entity with its constitution and congress. The states are divided into municipalities, the smallest administrative political entity in the country, governed by a mayor or municipal president (presidente municipal), elected by its residents by plurality.