During the 1930s and into the 1940s, up to 2 million Mexicans and Mexican-Americans were deported or expelled from cities and towns across the U.S and shipped to Mexico. According to some estimates, more than half of these people were U.S. citizens, born in the United States.

It’s a largely forgotten chapter in history that Francisco Balderrama, a California State University historian, documented in “Decade of Betrayal: Mexican Repatriation in the 1930s.” He co-wrote that book with the late historian Raymond Rodriguez.

“There was a perception in the United States that Mexicans are Mexicans,” Balderrama said. “Whether they were American citizens, or whether they were Mexican nationals, in the American mind, that is, in the mind of government officials, in the mind of industry leaders, they’re all Mexicans. So ship them home.”