The American left was once in love with the labor movement. Take, for example, the careers of this quartet of famous progressives: Margaret Sanger, John Steinbeck, Betty Friedan, and Martin Luther King Jr. All were committed to audacious reform and had the ability to turn their political passions into memorable prose. And all believed, at critical times in their lives, that a powerful union movement was essential to making their nation a more decent, more egalitarian society.

Sanger turned birth control from a furtive, underground pursuit into an international movement. But she began her activist career as a supporter of the militant Industrial Workers of the World, at one point helping to lead a temporary evacuation of IWW strikers’ children from a Massachusetts milltown so impoverished that few of the kids wore underpants. Steinbeck wrote his classic novel Grapes of Wrath after working closely with a radical union of farm and packing-house workers. California agribusinesses and their favored legislators tried, in vain, to get his book banned from public libraries. Before Friedan published The Feminine Mystique, she reported for the house organ of the United Electrical Workers, a union then led by communists, on the lack of good wages and child care for working women. After the Montgomery bus boycott, King forged a bond with such pragmatic social democrats as Bayard Rustin, A. Phillip Randolph, and Michael Harrington, who sought to build a durable alliance between the civil-rights movement and the AFL-CIO. King was murdered while aiding a strike by black sanitation workers to persuade the city fathers of Memphis to recognize their union.

There once would have been nothing surprising about the pro-labor sympathies of the famous four. From the Gilded Age into the 1960s, nearly every left-wing thinker and activist placed his or her faith for far-reaching social change on the fortunes of the union movement. Only when wage earners built strong institutions to fight for their interests would politicians take steps to markedly improve the lot of the American majority.

In the 1930s, this belief inspired intellectuals like Edmund Wilson, composers like Aaron Copland, painters like Jacob Lawrence, and photographers like Dorothea Lange to create art of sustained brilliance. It also helped gain support for mass strikes and organizing drives that eventually forced legislators to act. In 1934, labor radicals spearheaded shutdowns in Minneapolis and San Francisco that mushroomed into general strikes. A year later, Congress, alarmed that the unrest might imperil economic recovery, passed the Wagner Act—the landmark bill that, for the first time, set up an agency, the National Labor Relations Board, to protect the right of workers to have a union of their choosing. In 1938, lawmakers added the Fair Labor Standards Act, which established a national minimum wage and prohibited most forms of child labor. By the mid-1950s, one third of all wage earners belonged to a union.

But gradually, many progressives and labor unionists soured on one another. The AFL-CIO leadership’s backing for the Vietnam War and the class tensions provoked by both the counterculture and the environmental movement had something to do with it. So did the shift of young leftists from fighting to remedy economic injustice to battling discrimination based on race, gender, and sexual orientation. Meanwhile, groups with lavish resources like the U.S. Chamber of Commerce and the Atlantic Legal Foundation moved aggressively to undermine enforcement of the Wagner Act. That thousands of workers got fired every year for trying to organize unions fails to gain much attention, even in left-wing periodicals and websites.

By the 1980s, hundreds of progressives did break out of the countercultural cocoon and go to work for labor—as organizers, publicists, and in-house educators. The new breed included Karen Nussbaum, a feminist whose Boston-based group Nine to Five recruited women office workers; and Bill Fletcher Jr., a black socialist hired as education director of the AFL-CIO. Andrew Stern, who became head of the Service Employees International Union, had come to college in 1968 expecting to study business but instead joined a series of radical movements.

These activists, together with rank-and-filers frustrated by the old guard’s failure to reverse labor’s dwindling power at the workplace, brought a new spirit and imagination to their tasks. “Put the movement back in the labor movement,” they plastered on bumpers and protest signs. They mounted “corporate campaigns” grounded in intensive research that compelled anti-union firms to explain their skirting of environmental, safety, and overtime pay laws. They also aligned their unions with opponents of Ronald Reagan’s interventions in the Third World.

In 1995, the labor left helped elect John Sweeney president of the AFL-CIO, hoping the white-haired veteran of union wars and his “New Voice” team could reverse the movement’s long slide. Their academic allies staged a series of crowded teach-ins featuring speakers such as Betty Friedan, the philosophers Richard Rorty and Cornel West, and the historian Eric Foner. “I have a pretty good Geiger counter,” announced Friedan, on returning to what had been her original cause, “and that counter is clicking again, because I think we are on the verge of something new.”

Despite this fresh energy, labor continued its long decline. The new breed of union activists failed to change the popular image of leftists forged in the 1960s—college-educated rebels who had little in common with ordinary Americans. The cross-class insurgency in Wisconsin that is defending the bargaining rights of public employees is a heartening exception. But it has not yet spawned a national movement to defeat conservative attempts to turn unions into toothless institutions, both at the workplace and in politics.

Today, perhaps, labor’s beleaguered champions should take a bit of inspiration from their own past. The first celebration of Labor Day occurred in New York City in 1882. Twenty thousand unionists paraded before a quarter-million cheering spectators. Planners boasted that the event would “show the strength and esprit de corps of the trade and labor organizations” and “warn politicians that they shall go no farther in pandering to the greed of monopoly and reducing the condition of the masses.” Their language sounds archaic. But during the current rerun of the Gilded Age—when corporate profits are soaring and unemployment remains obscenely high—an updated version of that kind of protest would be an excellent idea.