What are the most powerful unions in America?

About 10% of workers belonged to a union in 2019

Since the predecessors of today's labor unions began forming in the late 1800s and wading into politics in the 1900s, unions have waned in power compared to their mid-century heyday but still represent millions of American workers.

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The AFL-CIO is the largest union federation in the U.S., made up of 55 national and international unions with 12.5 million members worldwide. Its member unions span from the Actors Equity Association to the Utility Workers Union of America.

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Other massive unions include the National Education Association, which has 3 million members; the Service Employees International Union, which has roughly 2 million members in the U.S. and Canada; the International Brotherhood of Teamsters, which has 1.4 million members in the U.S. and Canada; and the United Auto Workers, which has more than 400,000 active members and 580,000 retired members in the U.S. and Canada.

Local 598 Flint Assembly worker Dawn Dekalita cheers outside of Flint Engine South in Flint, Mich., on Friday, Oct. 25, 2019. (Ryan Garza/Detroit Free Press via AP)

The UAW is the most recent major private-sector union to strike on a mass scale. Nearly 50,000 General Motors employees walked off the job for more than a month demanding better pay raise structures and more opportunities for temporary workers to go full-time.

Union membership dipped slightly in 2019, according to the Bureau of Labor Statistics, despite an uptick in the number of Americans who approve of labor unions. About 10.3 percent of workers, or 14 million people, belonged to a union in 2019, according to BLS.

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That's compared to 1954, when union membership peaked at 28.3 percent of American workers, according to the Congressional Research Service.

Politicians court union endorsements, especially in crucial presidential election years like 2020. The AFL-CIO endorsed Democratic presidential nominee Joe Biden in May, calling him a "lifelong supporter of workers."

Richard Trumka, president of the AFL-CIO, speaks to members of the news media as he departs after a meeting with U.S.President-elect Donald Trump at Trump Tower in New York, Jan. 13, 2017. (REUTERS/Mike Segar)

“The path to the presidency runs through the labor movement,” AFL-CIO President Richard Trumka said in a statement. "And with the full force and unmatched reach of our political program, we are ready to pave that road for our friend Joe Biden."

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Unions have also been notorious for corruption among officials, leading to some sudden shakeups in leadership. Prosecutors charged former UAW president Gary Jones with corruption in March, alleging he conspired with other union leaders to embezzle money.

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