By Katie Reilly
September 2, 2016

As the U.S. celebrates Labor Day weekend, the holiday heralds the start of a new season—the return to school, the retiring of summer whites. But its history is rooted in celebrations of the American worker and support for workers’ rights.

Here are some of the most important moments in the history of Labor Day:

New York City’s “monster labor festival”

Before becoming a national holiday, Labor Day was celebrated in individual states. Among the first were New York, New Jersey and Colorado, which approved the holiday in 1887, according to the U.S. Department of Labor.

But even before then, the holiday’s origins are evident in parades and picnics that supported labor issues and workers’ rights. Linda Stinson, a former historian for the U.S. Department of Labor, described one parade in particular as “pivotal” to the holiday’s history: Various unions in New York City joined together for a “monster labor festival” on Tuesday, Sept. 5, 1882. Ahead of the celebration, the Central Labor Union passed a resolution, declaring that “the 5th of September be proclaimed a general holiday for the workingmen in this city.” An estimated 10,000 people marched in the parade, many losing a day’s pay in order to participate.

Read more: How Labor Day Was Celebrated When Unions Were on the Rise

A national peace offering

Labor Day became a federal holiday in 1894, established by President Grover Cleveland as an election-year concession to union workers, who had reason to be upset with him following a deadly railroad strike.

Workers for George Pullman’s sleeping car company had staged a strike after Pullman cut their wages but kept their rent prices at the same rate. The 150,000 members of the American Railway Union showed their support by refusing to work on trains carrying Pullman cars. The strike became a national issue that disrupted train traffic across the country, prompting Cleveland to dispatch troops to Chicago to end the strike. The confrontation led to riots, and many of the protesters were wounded or killed. TIME later called it “one of the bloodiest strikes in U.S. history.”

A bill establishing the holiday was quickly approved by Congress, according to PBS News, and Cleveland signed the bill into law, hoping to appease the nation’s workers. (He ultimately lost his bid for reelection anyway.)

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The World War II effort: “Free labor will win”

The unemployment rate fell dramatically during World War II, dropping from 14.6% in 1940 to 1.2% in 1944, when American workers were responsible for aiding the Allies through the production of planes, tanks and guns. In a way, the fate of the world was in the hands of American labor—and Labor Day was celebrated accordingly.

The role of labor in wartime was highlighted by messages like this one, from the Workers of America, which celebrated Labor Day in 1942 by saluting those involved in producing war materials:

“American labor salutes the great war production job already done, dedicates itself to the still greater job ahead and throws this challenge to the Axis: that freedom of the individual to think and speak and worship and work shall no perish. Free labor will win,” declared the film reel.

While the number of laborers grew, the wartime period also stoked the beginnings of a backlash against unions, as workers felt pressure to meet higher production demands without a wage increase. Many unions also did less to protect the rights of the greater numbers of African-Americans and women who joined the workforce during the war. Still, by 1945, a record 35.5% of the non-agricultural workforce was unionized, as the organized labor force grew from 10.5 million members in 1941 to 14.75 million in 1945, according to the Economic History Association. By comparison, the union membership rate was 11.1% in 2015, according to the Bureau of Labor Statistics.

Write to Katie Reilly at Katie.Reilly@time.com.

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