The Mexican Repatriation was the mass deportation of ½-2 million people from the United States to Mexico between 1929 and 1936.American Widely blamed for exacerbating the overall economic downturn, Mexicans were further targeted because of "the proximity of the Mexican border, the physical distinctiveness of mestizos, and easily identifiable barrios."
Estimates of how many were repatriated range from 500,000 to 2,000,000, of whom 60% were US-born citizens. Because the forced movement was based on race, and ignored citizenship, one scholar has argued that the process meets modern standards for ethnic cleansing.
In 2005, the State of California passed the "Apology Act for the 1930s Mexican Repatriation Program", apologizing for the state government's role in the repatriation.
At the beginning of the Great Depression, there were two primary sources of US residents of Mexican descent: territorial changes after the Mexican-American War, and migration.
With the U.S. victory in the Mexican-American War, the Gadsen Purchase, and the annexation of the Republic of Texas, much of the present-day states of California, Nevada, Utah, New Mexico, Arizona, and parts of Texas, Colorado, and Wyoming, were ceded to the United States. This land was 45% of Mexico's pre-war territory.
80-100,000 Mexican citizens lived in this territory, and were promised U.S. citizenship under the Treaty of Guadalupe Hidalgo, which ended the Mexican-American War. About 3,000 of the total 80,000 decided to move to Mexican territory. Mexicans who remained in the U.S. were considered U.S. citizens and counted as white on the U.S. census until 1930; however, the majority European population often treated them as foreigners.
By one estimate, in 1900, about 500,000 people of Mexican ancestry lived in the US, of whom 400,000 had been born in the US.
Mexican emigration was not significant until the construction of the railroad network between Mexico and the Southwest, which both provided employment and eased transit. Increasing demands for agricultural labor, and the violence and economic disruption of the Mexican Revolution, also caused many to flee Mexico during the years of 1910-1920 and again during the Cristero War in the late 1920s.