Workers in 58 cities from Boston to the coast of California walked off the job this morning at McDonald’s, Wendy’s, Burger King, and other fast-food retail stores. Labor groups said employees from Macy’s, Sears, and Dollar Tree would likely join the strike, too. The labor strife follows short strikes by fast-food workers in New York City, Chicago, Kansas City, Detroit, and other cities this summer, protesting low wages and working conditions.

As a few hundred strike supporters overwhelmed a McDonald’s near the Empire State Building on Wednesday, advocates for low-wage workers are asking Congress to raise the federal minimum wage from $7.25, set in 2009, to $9 an hour. Workers are also demanding $15 per hour as a new wage, which comes to $15,000 per year for a full-time job.

McDonald’s and Burger King Worldwide stated on Wednesday that independent franchises control wages in most of their restaurants in the United States. The National Restaurant Association also told the Associated Press that low wages are defensible given that fast-food workers tend to skew younger with little to no work experience. “The median wage [for service workers] of $9.08 an hour still falls far below the federal poverty line for a worker lucky enough to get 40 hours a week an never have to take a sick day,” Scott DeFife said. "Most fast-food workers earned more than the minimum wage and… many of the jobs were held by students and part-timers.”

However, four of five low-wage workers in America are at least 20 years old, with many workers trying to support a family on income defined by the federal government as poverty. In the “new economy” trailing the Great Recession, some 3.8 million American workers earn minimum wage or below, most of them adults and not teenagers.

The workers are also demanding the right to organize and form unions. “Workers are still facing unlawful practices in response to their organizing, including terminations, reduction of hours, threats of retaliation and many other unlawful actions intended to discourage employees from organizing but workers aren’t giving up the fight,” Fast Food Forward, a labor group representing the workers, said in a statement.