Tipping is racist.

That's the argument being forwarded by some liberal activists and politicians as a way of stigmatizing laws that exempt certain professions, mainly restaurant workers, from the federal minimum wage.

However, there is little historical evidence for the argument.

"I don't think tipping was particularly racial … It was more a matter of customers showing off their wealth," said Gerald Friedman, professor of economics and history at the University of Massachusetts at Amherst and associate editor of the scholarly journal Labor History.

Nevertheless, activists pushing for a higher minimum wage have pushed the argument now that their movement has gained ground. Nineteen states are set to phase in higher minimum rates this year, according to the National Conference of State Legislatures. That has brought more attention to the exception for tipped employees in most minimum wage laws. Those employees, mostly in the service industry, can legally be paid less the standard minimum on the grounds that their tips make up for it.

Minimum wage fans have argued that that's not merely wrong but a vestige of 19th racism. Minneapolis Mayor Betsy Hodges said in a February op-ed that "tipping as an institution is rooted in the history of slavery." Hodges has advocated that her city adopt a $15 minimum wage that would not allow exceptions for tips.

"The notion of tipping is not native to America, but was imported from Europe just as slaves were emancipated. At that time, restaurants and railroads insisted that the now-former slaves who were working in those industries were not worthy of earning a wage and should subsist on the kindness of customers' tips alone," she said.

Shake Shack franchise founder Danny Meyer, who has prohibited tipping at his restaurants, made a similar claim in a January speech at New York's Manhattanville College.

Meyer said the restaurant and railroad industries "successfully petitioned the U.S. government to make a dispensation for our industries that we would not pay our servers" and have them rely on gratuities instead. "And no surprise, most of the people who were working in service professional jobs and restaurants and in Pullman train cars were African-American."

It is not clear what action Meyer was referring to. The first federal minimum wage law, which included an exception for tipped employees, passed in 1938 as part of President Franklin D. Roosevelt's New Deal.

Hodges and Meyer were both apparently citing claims of the Restaurant Opportunities Center United, a labor-backed nonprofit activist group that has been a major advocate of the $15 minimum wage.

ROC United co-director Saru Jayaraman said in a 2015 op-ed for the New York Times that the minimum wage had an "ugly, racialized history." She said that 19th century restaurant owners and railway companies fought legal efforts to outlaw tipping "especially since many of their workers were African-American, in many cases freed slaves whom these employers resented having to pay at all."

She repeated the comments in 2016 interviews with outlets such as the Washington Post and Mother Jones and in a recent book. Her claims have been advanced in places such as the comedy site Cracked.com.

ROC United did not respond to a request from the Washington Examiner to provide historical citations for the claim or to identify any economists or historians who could back it up.

Friedman says it is true that the practice of tipping was largely imported from Europe. It began with wealthy Americans imitating aristocrats who they met while traveling abroad. There is little evidence that employers first promoted tipping, he says.

There was a racial aspect to tipping in the U.S. in that the recipients of tips were typically people in service-related jobs, where African-Americans often found employment. However, women and the Irish were also common in those professions, Friedman noted.

"It was probably more of a gender thing than a racial thing," he said.

It wasn't until the end of the 19th century that some employers began to realize that tipping worked to their advantage because it allowed them to pay lower wages. Railroads in particular took advantage of that. But by that point tipping had become common, Friedman said.

"The companies were happy to take advantage of it once they saw what was going on," Friedman said.

Tipping was controversial throughout the 19th century. Many people resented having to pay tips, viewing it as a form of extortion. Others viewed it as a degrading practice that was "un-American."

Many companies actively discouraged workers from requesting tips, viewing it as a nuisance to customers, notes Tipping: American Social History of Gratuities by Kerry Segrave. The 1998 book appears to be one of few historical studies done on the issue.

"Prominently displayed on the Cunard line ships was a notice asking that … any demands from (stewards) for tips be reported to management 'so the matter can be dealt with,'" Segrave writes.

The New York Central Railroad issued similar instructions starting in the 1890s. New York City movie ushers went on strike in 1919 because management discouraged customers from tipping.

Many states in the early 20th century passed laws that prohibited tipping altogether. Those included southern states such as Mississippi in 1912, Arkansas in 1913 and South Carolina, Tennessee and Georgia in 1915. In 1910, Washington D.C., made it illegal for the city's waiters to accept tips.

"The fact that the states made the practice illegal weighs against the race argument," Friedman noted. The laws were eventually repealed because of widespread noncompliance.