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President Barack Obama speaks in Washington, D.C. about a failed procedural vote on a bill to raise the minimum wage to $10.10 an hour. - 

President Obama wants lawmakers to raise the federal minimum wage from $7.25 to $10.10 an hour.  But Congress hasn't voted to increase the minimum wage since 2007, and there’s little hope it will now.

It’s a different story at the local level.

In just the last year, Seattle and San Francisco both passed measures to gradually increase their minimum wages to $15.  And the Los Angeles City Council is considering a $15.25 wage.

Those cities are following in the footsteps of SeaTac, Washington, a tiny town just outside Seattle, and home to the region’s biggest airport. A year ago, it became the first city in America to have a $15 minimum wage.

“SeaTac will be viewed someday as the vanguard, as the place where the fight started,” union organizer David Rolf, who led SeaTac’s $15 campaign, said in a victory speech in November 2013.

That day is already here, but the funny thing is Rolf never set out to raise SeaTac’s minimum wage, much less start a national movement. His original goal was to unionize workers at Sea-Tac airport.

When employers – led by Alaska Airlines – played hardball, Rolf put a $15 minimum wage proposition on the city ballot as leverage.

It won by just 77 votes.

“Things could have gone very different had the airlines said we’ll bargain a contract,” Rolf says. “Those workers may have had $15, but it might not have been on the ballot. It would have been in the union contract, and it would have just been for those workers.”

As it turns out, because of a court challenge it’s actually those airport workers who are the only ones in SeaTac not making at least $15 an hour. But the $15 minimum wage movement soon spread, to Seattle last June, and to San Francisco in November.

“It was not yet with an eye on being some sort of domino that fell and leveraged similar victories across the country, but I think people are proud that that’s what happening,” Rolf says.

And surprised, says Peter Dreier, a professor of politics at Occidental College.

“A couple years ago the idea of a $15 minimum wage would have been considered outrageous,” Dreier says.

So what changed?

There’s the $15 number itself, nice and round, easy to fit on a bumper sticker. The figure first came to people’s attention in a series of strikes by fast-food workers that started in 2012. The workers didn’t achieve their goal of unionization, but $15 stuck.

There’s also the fact that post-recession, many voters have become more concerned about income inequality, says Paul Sonn, the National Employment Law Project’s general counsel.

“It’s clearly a response to the economy’s tilt to low-wage jobs, which is hitting cities like L.A. hard, which are seeing wages flat or falling but at the same housing and living costs are continuing to rise,” Sonn says.

Unions say they hope the $15 wage can spread to every state, but labor historian Nelson Lichtenstein is skeptical. “I don’t think having high wages in a few cities will mean it will spread to red state America,” Lichtenstein says.

Oklahoma recently banned any city from setting its own minimum wage, joining at least 12 other states with similar laws.

In November, voters in four Republican-leaning states – Alaska, Arkansas, South Dakota, and Nebraska – did approve higher minimum wages, but they weren’t close to $15.

Having a patchwork of local wage standards is bad for workers, Lichtenstein says.

“One of the laws of labor history is that you can’t a strong movement in one place and have the rest of the country hostile to it,” he says. “Eventually the strength of that labor movement will be drained away as employers do in fact move.”

Whether local minimum wages cause businesses to pack up and move somewhere cheaper is hotly debated among economists.

A University of California, Berkeley study predicts small clothing manufactures could leave L.A. if the minimum wage is hiked. But no one really knows, because the $15 wage movement has just gotten started.