The United States' entrance into World War II created unprecedented demands for labor across the nation. Mexico's economy, by contrast, did not experience the wartime boom to the extent of its northern neighbor. As labor demand outstripped labor supply in the U.S., and Mexico's economy remained relatively sluggish, trans-border labor migration increased dramatically. Many of these migrants arrived in the United States via the Bracero Program--a migratory labor agreement between the two nations initiated in 1942. However, a significant portion of the migrant workers circumvented the program and entered the United States without documentation. These undocumented workers easily found employment in the labor-starved agricultural sector of the American Southwest.
In the post-war years, cultural and economic trends combined to cool the undocumented migrant workers' welcome in the United States. The return of American servicemen into the labor pool following World War II and the Korean War, Cold War era fears of communist infiltration across an unsecured border, and an economic downturn in 1954 led to one of the most dramatic crackdowns on undocumented immigrant labor in United States history. Beginning in 1954, the Immigration and Nationalization Service (INS)--under the leadership of retired U.S. Army Lieutenant General Joseph "Jumpin" Joe Swing--employed its border guard to forcefully deport all undocumented workers in the southwestern border states. In the two years that followed, the INS engaged in the forced deportation of approximately 3.5 million immigrant workers in an official government project named Operation Wetback.*
To learn more about this program, we'll begin with a literature review and then delve into research in newspapers and census materials:
*In the 1940s and 1950s, the term "wetback" was commonly used in the press and official government parlance. It reflects the differing cultural sensitivities of the era; slurs against many racial and ethnic groups were not uncommon at the time. The derogatory term "wetback" was first used in the 1920s to describe individuals who crossed the Rio Grande River to enter the United States, often in search of jobs as agricultural laborers. The use of "wetback" here is simply in the interest of historical accuracy. If you are searching in sources published recently, terms like "undocumented worker" are more likely to be effective.