The program, which took its name from the Spanish word for arms - brazos - was initiated in 1942 to replace American field workers who went to fight in World War II. After the war, farmers lobbied the government to keep the program going until 1964.
Wikipedia: Bracero Program
And here's the Smithsonian's Opportunity or Exploitation: The Bracero Program.
Before starting new guest worker programs, we should evaluate the one that happened before.