With a population of more than 20 million in the greater metropolitan area, you can expect to find all kinds of people in Mexico City, in terms of racial, sexual, political, cultural and wealth diversity. Citizens are mostly Mestizo (people of mixed European and Amerindian racial background) and white. Amerindian people constitute less than one percent of the city's population, but there are some who are still moving to the city in search of opportunities. As elsewhere in Latin America, socioeconomic status tends to be highly correlated with ethnicity in Mexico City: by and large, the upper and middle classes have more European ancestry than the poor and the lower classes.
The Mexican–American War was a conflict that sparked when the . annexed Texas in 1845 and the Mexican government refused to recognize the secession of Texas which was the precursor to the annexation.  The war, which began in 1846 and lasted for two years, was settled via the Treaty of Guadalupe-Hidalgo which led to Mexico giving up even more of its land to the ., including California.  Mexico further transferred some of its territories (southern Arizona and New Mexico ) to the . via the Gadsden Purchase in 1854.