The fast food strike wave that hit seven cities last month is going nationwide today as workers in more than 50 cities—and hundreds of chain restaurant locations—walk out to protest low wages.

As has been the case in previous efforts to organize, low-wage workers are demanding a living wage of $15. (That's a substantial step-up from the national minimum wage, which falls at $7.25; according to the Economic Policy Institute, the lowest-earning 20 percent of U.S. workers still earn less than $9.89.) But today's action appears to be bigger, and wider-reaching, than any in recent memory.

Here's what to know—and why to care.

It's the largest U.S. fast food strike ever.

As far as we know, that is.

Salon describes today's action as "the largest-ever mobilization against [the] growing, low-wage, non-union industry, which until last fall had never faced a substantial U.S. strike." That took place in New York last November and coincided with a massive effort to unionize fast-food workers, which was supported by civil rights and community groups and, unlike previous efforts, strived to unite workers at McDonald’s, Taco Bell, Wendy’s, and various other chains in the city.

It's now a nationwide movement.

This is almost certainly the most widest-reaching fast-food action, geographically speaking. The movement can be traced back to last November's one-day strike in New York. Then came a slew of one-day strikes that extended beyond New York and into various Midwestern cities—Chicago, Kansas City, Detroit, St. Louis, and others—earlier this summer.

Today's actions are even bigger. As The Nation reports, the movement has spread to Los Angeles, Milwaukee, Raleigh, and Memphis, thanks to assistance from the Service Employees International Union (SEIU). In other words, it's no longer a regional thing—it's a national effort.

The South is getting involved.

That's a big deal in and of itself. The Southern states lag behind those in the North in unionization; for example, about 24% of New York workers are unionized, a figure that snakes down to 2.9% in North Carolina. That reality, coupled with right-to-work laws in the region, has posed a huge obstacle to organized labor.

But MSNBC reports that the summer's actions have been a turning point, even in the South:

“You would think it would be very hard to organize, because [North Carolina] is a right-to-work state and because people have been living under fear of being fired for the most minute issue … but to be honest with you, people are just fed up,” said Corine Mac, a Charlotte-based community organizer affiliated with the NAACP, Center for Community Change and the A. Phillip Randolph Institute.

Dearius Merritt, a striking Church’s Chicken assistant manager in Memphis, Tenn., also described fast food workers in his city as “fed up.”

It's also a feminist movement.

According to the Bureau of Labor Statistics, women comprise two-thirds of fast-food workers. Many are struggling to raise a child on their wages. 

Dig deeper, and the gender disparity is more disturbing than it appears. Sally Kohn writes today in The Daily Beast that the bulk of minimum-wage earners in the fast food industry are women of color, who tend to earn 60 percent less than what men make. Swiftly replacing the popular image of the glass ceiling with the less glamorous reality of the "sticky floor" that greets such women every morning, Kohn argues that "a labor market that increasingly includes women at the same time that wages are being deliberately driven into the ground creates a disastrous economic and moral trap for millions of women."

Today, some protest signs are addressing gender:

The industry encapsulates the nationwide gap between corporate earnings and employee wages. 

As The Nation sums it up, paraphrasing Wisconsin organizer Mike Wilder, the strike is about "holding profitable companies accountable for not paying workers enough to afford basic amenities like food and rent." The magazine spotlights workers like Angela Gholston, a McDonald's employee in Detroit who now receives Medicare because she can't afford to buy in to the company's healthcare plan.

Or, consider the story of Willietta Dukes, who is striking today—for the first time—in North Carolina. She makes $7.85 as a guest ambassador and team leader at Burger King. Last month she lost her house. Her hours were slashed. Now she lives out of her 20- and 21-year-old sons' guest bedrooms. "Burger King says they can't pay employees like me higher wages because it would force them out of business," she writes. "Yet last year it made $117m in profits and its CEO took home $6.47m."

Low Pay Is Not OK, an organizing site for the campaign, claims that the eight biggest fast food companies earned a combined $7.35 billion last year. Its annual salaries for workers often amount to $11,200. With figures like that, the fast food industry neatly sums up the gap between corporate earnings and nearly unlivable wages. 

It's not just about fast food.

The industry is perhaps the country's biggest low-wage offender. But the movement for a living wage extends beyond that sphere, as it well should.

In recent months, liberal publications like The Nation have been focusing its attention on Walmart, which makes sense: the multi-billion dollar corporation is the nation's largest employer and pulls in more than a billion dollars annually. It pays its employees an average hourly wage of $8.81. (You'll recall that The Nation's gripe with Walmart came to a head earlier this month when the latter called out the former for its stipend-paying internship program.) 

A local organization, Living Wage NYC, points out that New York City's living wage law excludes "employees who work in privately-owned, publicly-subsidized developments." Meanwhile, Labor Secretary Thomas Perez says now that the strikes are another reason to raise minimum wage nationwide.

To succeed, the largest fast food strike ever will have to take into account more than just McDonald's and Wendy's.

Service will probably be slow in fast food restaurants today. 

If you still don't care about the strikes, well, all we can say is to be prepared to wait an extra 15 minutes for your McDonald's chicken wing monstrosities. Maybe let your fellow customers know the reason for the delay.