Solidarity forever,

Solidarity forever,

Solidarity forever,

For the union makes us strong.

Folksinger Pete Seeger made that tune "Solidarity Forever" famous in the 1950s. But the words union and labor have taken on a much charged meaning since then.

On Monday markets will close and businesses will shut in commemoration of Labor Day, a national holiday for 119 years. Working hours and conditions for workers have undoubtedly improved over that time but the labor movement itself has shrunk substantially. Only 11% of U.S. workers are unionized compared to over 30% in the 1950s and over 20% in the 1980s, according to the Bureau of Labor Statistics.

Now public workers—teachers, police and firefighters—account for 36% of the unionized labor force and private sector workers less than 7%. Given these figures and the growing number of layoffs of public sector workers, the future does not look bright for unions in America.

Related: McDonald's Should Share Billions in Profits with Workers: Labor Organizer

But labor organizer Kendall Fells who led striking workers in New York City during Thursday’s nationwide one-day strike of fast food workers, says it looks like the labor movement is getting a “second wind…You see the labor market starting to get its swagger back.”

Fast food workers in about 60 cities around the country stayed off the job Thursday, demanding a wage of $15 an hour and the right to organize without retaliation from their employers. But today they are back at work, most of them earning the minimum wage of $7.25.

Related: Why We Need Labor Unions After All

Fells says the momentum is growing for the labor movement, at least among fast food workers. The one-day strike rollout started in New York City in November, then expanded to 7 cities and now 60 cities. He says these workers are “fed up” with low wages and willing to do something about it, which will help the economy overall.

“The union is what created the middle class in this country and the union is what’s going to bring it back,” says Fells, organizing director for Fast Food Forward, which is affiliated with the SEIU.

Related: The Labor Market Is in Worse SHape Than You Think

Full-time unionized workers had median weekly earnings of $943 in 2012, or about $49,000 annually compared to $742 (about $38,600 annually) for nonunion workers, according to the BLS. But despite that 21% difference, only 54% of Americans approve of labor unions, according to a recent Gallup poll. That’s slightly higher than the 52% in polls from 2010, 2011 and 2012, but below the 62% historical average since 1936.