Tipping is a norm in the United States—and it's always been controversial. The practice took off after the Civil War, as employers sought cheap labor from formerly enslaved people: if tips were expected, companies could get away with paying laughably low wages. But the practice was always controversial, and has been vehemently challenged since it first came to the U.S. from Europe. We speak with Nina Martyris, a journalist who's written about the history of tipping in the United States, to find out how tipping—once deemed a "cancer in the breast of democracy"— went from being considered wholly un-American to becoming a deeply American custom.