When racist progressives in the early 1900s pushed for the minimum wage, they understood its impact: keeping blacks and immigrants out of the workforce by making it illegal for them to out-compete white Americans on the price of their labor.

Today’s progressives aren’t bigots, but the policy they’ve successfully championed — a $15 minimum wage that will take effect in New York City in 2019 — will have the same effect it had a century ago: making it difficult for marginal workers to find employment.

Consider the car-wash industry. These days, 90 percent of new car washes in the United States are fully automated exterior washes with free do-it-yourself high-powered vacuums for cleaning inside the vehicle. Some customers like this model, but men wielding hoses and rags actually do a more thorough job than the very best machines.

Car washes automated because they couldn’t find enough reliable employees willing to work for less than it costs to install hot-air blowers and banks of spinning brushes.

In New York City, it’s a different story. Here, we’re lucky to have a large population of immigrant workers — many of them illegal — willing to do the sort of dirty work that most of us natives avoid. So car washes in the Big Apple tend to have fewer machines and more men. Yes, these jobs involve repetitive work for low pay.

But they’re often better than the alternatives.

During my reporting, I met a 35-year-old gynecologist from Nigeria working at a car wash in Canarsie. The job is helping to pay the bills while he works toward his US medical license. Then there’s the 74-year-old Haitian immigrant, who survives on Social Security but likes keeping busy and supplementing his income cleaning vehicles.

Many more so-called carwasheros in New York City are raising families, subsidizing their meager incomes with Medicaid, food stamps and the Earned Income Tax Credit.

How does taking away their jobs make them better off? The $15 minimum will push New York car-wash operators to automate like the rest of the country, denying workers the right to undercut the machines on cost.

It’s already starting to happen.

Amir Malki, a leading car-wash equipment installer in the region, says over a dozen car-wash operators in New York City have inquired about putting in equipment to eliminate workers.

One owner told me he’s thinking of purchasing $300,000 in equipment that will allow him to eliminate 15 of his 22 men. That’s because when the minimum wage goes from $9 to $15, he’ll have to charge at least $25 per car wash to make a profit — and few will pay that much.

If he automates, quality will suffer but he can lower his price to about $8. “That’s the only way I can think of to survive,” he says.

Veteran car-wash operator Martin Taub owns three New York City locations. One is automated, another is about to be sold off in a real estate deal and the third is full-service — but not for long. Taub is planning to install machines at that location as well, thanks to the $15 minimum.

Those lacking the capital or credit to fully automate can also purchase equipment piecemeal. One option is to install a Dry ’N Shine — a giant spinning wheel wrapped in absorbent material that rolls over the vehicle to sop up moisture.

Equipment installer Malki says the machine can eliminate as many as six men. But it costs about $70,000 including installation, so prior to the passage of the $15 minimum, his New York City clients have mostly held out. “They’ll come around,” says Malki.

Progressives claim they’re fighting for “economic justice,” which is ironic. “Every worker, regardless of what they do or where they came from, is entitled to be treated with dignity and respect,” said the Retail Wholesale and Department Store Union’s president Stuart Appelbaum in a speech about the carwasheros last year.

Is it more dignified to have a difficult job or no job at all? In keeping with progressivism’s long history of infantilizing the poor, Appelbaum and his allies don’t respect the right of the carwasheros to make that choice for themselves.

Adapted from “Minimum Wage vs. the Carwasheros,” available at Reason.com, where Jim Epstein is a writer and producer.