To keep women and minorities unemployed. LA Times:
“In 1910, 22% of the U.S. workforce was foreign-born. A Who’s Who of American economic reform warned that immigration was leading to “race suicide,” what President Theodore Roosevelt in 1907 called the “greatest problem of civilization.” This race suicide theory claimed that because non-Anglo-Saxon immigrants had low living standards, their competition in the labor market undercut the wages of the American workingman. The key assumption was that Anglo-Saxon natives were more productive, but that immigrants worked cheap. As Stanford sociologist and avowed nativist Edward A. Ross put it, “the coolie, though he cannot outdo the American, can underlive him.” Woodrow Wilson, echoing many others, said that Chinese immigrants could “live upon a handful of rice for a pittance.” Similar charges were made against Jews and Catholics arriving from southern and eastern Europe.
The American-born worker, who refused to lower his family’s living standard to the immigrant’s level, opted instead to have fewer children. Thus, concluded the theory, the inferior races would outbreed and displace their white Anglo-Saxon betters.
Progressive economists proposed a minimum wage as the ideal remedy. It lifted up the deserving while excluding the unworthy and did both in the name of progress. Journalist and progressive social reformer Paul Kellogg in 1913 advocated a minimum wage of $3 per day for all immigrants, double the $1.50 per day ordinary laborers were then paid. Kellogg knew that no firm would hire an unskilled immigrant for $3 per day. That was the purpose of his high minimum wage, as he wrote, to exclude “Angelo Lucca and Alexis Spivak” from American shores, thus protecting American jobs for “John Smith and Michael Murphy and Carl Sneider.””