Workers abided by a no-strike pledge until the end of the war. But afterward, they mobilized to seek higher wages and better conditions. The largest strike wave in U.S. history swept the country between 1945 and 1946, with more than 4 million workers walking off the job. Strikers included industrial workers, film crews and automotive and municipal workers. To put an end to the unrest, Republicans in Congress, with support from Democrats, passed the Taft-Hartley Act in 1947.

“Businesses and conservatives felt that unions had become too powerful,” said Dr. Joshua Freeman, a distinguished professor of history at the CUNY Graduate Center in New York. “It was a deliberate effort to rebalance in a pro-business direction.”

Taft-Hartley placed limits on unions’ rights to strike or boycott and led to “right-to-work” laws, under which employees were not required to join unions or pay dues, thus weakening a union’s bargaining power. Right-to-work laws are still in effect today across 27 states.

Taft-Hartley “helped spark an exodus from highly-unionized areas to less-unionized areas and made it very difficult to organize union strength in right-to-work parts of the country,” Dr. Freeman said.

The Wagner Act created the National Labor Relations Board, an independent federal agency responsible for enforcing labor laws. The N.L.R.B.’s influence began to wane after the passage of Taft-Hartley, and it has since become a political “weathervane” depending on the administration, Freeman said.

From the 1970s through the 1980s, business as usual underwent big changes. Market deregulation, free-market reforms, automation, globalization and the staunchly anti-union Reagan administration all contributed to the decline of unions during this period. Membership fell to less than 17 percent of workers, half the level in the 1950s. The trend continued, and by 2020, union membership was at 11 percent.

Today, growing resentment over hazardous conditions and burnout has brought unions back into the spotlight. “Unions are cool again,” Dr. Freeman said, especially among younger adults who came of age during the recession in 2007-2009. According to a recent Pew Research study, 69 percent of adults 18 to 29 and 58 percent of adults 30 to 49 view unions favorably, although the majority of union members are older. Younger people are also quitting their jobs at record rates, a trend that has been dubbed the Great Resignation, or what Dr. Freeman calls “individual general strikes.”

Efforts to unionize have swept the retail and hospitality sectors, including at Amazon distribution centers and Starbucks, where both companies have mounted aggressive campaigns to quash them.

A weakening of the National Labor Relations Board and labor laws created the conditions for this environment, Dr. Freeman said. “A lot of the rights that workers have under the law have become almost meaningless,” he said. “The central concept here is that the American workers have a right to engage in collective activity without reprisal. And this is just absolutely, routinely violated.”

House Democrats attempted to pass a bill earlier this year that would have increased protections for workers seeking to unionize and overridden right-to-work laws. The bill failed to pass the Senate and now is embedded in the stalled reconciliation bill.

At a time when income inequality is widening and CEO wealth is growing, the labor movement may be ready for a change. Essential workers (like wartime workers during World War II) have kept the economy flowing, and now, a tight labor market has given workers an edge.

“When the labor market is favorable to workers, workers act on their own behalf,” Dr. Freeman said. “One way is they just quit lousy jobs. And the second is they act collectively. They’re not scared, they’re not terrorized by the possibility that they won’t have a job. I think part of what we’re seeing is the impact of that labor market condition.”

ANNY OBERLINK, an intern at Retro Report, is a degree candidate in documentary filmmaking at CUNY’s Craig Newmark Graduate School of Journalism. This article first appeared in Retro Report’s free weekly newsletter. Subscribe and receive lessons from history in your mailbox. Follow us on Twitter @RetroReport.