From barbecues to short vacations to bargain hunting, many people in the United States celebrate Labor Day—the federal holiday honoring the American worker—by looking for ways to relax.

This year marks the 130th anniversary of the holiday, which is celebrated on the first Monday in September. While actions by unions in recent years to defend workers recall the holiday’s activist roots, the three-day weekend it creates has become a milestone in the lives of Americans celebrating the unofficial end of summer.

Here’s what you should know about Labor Day:

How did Labor Day become a federal holiday?

Its origins date back to the late 19th century, when activists first tried to establish a day to honor workers.

The first Labor Day celebration in the United States took place on September 5, 1882, in New York City, when about 10,000 workers participated in a parade organized by the Central Labor Union and the Knights of Labor.

The quality of life of workers declined as they moved from manual labor to factory work, while the quality of life of factory owners “skyrocketed,” says Todd Vachon, an assistant professor at the Rutgers School of Management and Labor Relations.

In the years that followed, some cities and states began to recognize Labor Day by law. President Grover Cleveland signed a law in 1894 declaring the day a federal holiday.

That same year, workers at the Pullman Palace Car Company went on strike after the car manufacturer cut wages without lowering rent in the company-owned town where workers lived near Chicago, Vachon said. More than 12 workers were killed after Cleveland sent federal troops to break up the strike, he said.

Cleveland’s move to make Labor Day a federal holiday is seen by some historians as a way to “make peace” with the working class, Vachon said.

What do Americans do on Labor Day weekend?

During the three-day Labor Day weekend, travelers crowd airports and highways to escape the end of summer, and home cooks prepare barbecues for family and friends.

Barbecue has been a part of Labor Day celebrations from the beginning, says Robert F. Moss, food critic, culinary historian and author of “Barbecue: The History of an American Institution.”

He said it was already such a deep-rooted tradition in the U.S. that when labor movements emerged in the late 19th century, it was a natural way to celebrate in large groups. In the 20th century, barbecues on the holiday became more like backyard gatherings of friends and family, he said.

“There is still a lot of that sense of community when you gather around the grill and eat together,” he said.

Vachon said whether the celebrations remind you of the origins of the labor movement depends on whether you live in a place with a large union presence.

In Chicago, a parade and festival will be held over Labor Day weekend in what is now the Pullman neighborhood, home of the holiday. Bob Reiter, president of the Chicago Federation of Labor, said the parade and festival they host will draw union members and their families from across the area.

How has the workers’ movement developed over the decades?

When Labor Day became a federal holiday in 1894, unions were widely controversial in the U.S. and courts often declared strikes illegal, leading to violent confrontations, Vachon says. It wasn’t until the National Labor Relations Act of 1935 that private sector workers were given the right to join unions.

Later in the 20th century, states also began to pass laws allowing unionization in the public sector. But even today, not all states allow collective bargaining for public employees.

In recent years there has been a revival of union organizing, activism, interest and support, Vachon said.

“Many of the millennials and Generation Z are coming into the job market at a time that is not much different than the 1880s, when there was a lot of labor unrest,” Vachon said. “The jobs just don’t pay enough for people to achieve the American dream.”

What is the connection between fashion and Labor Day?

The saying that you shouldn’t wear white after Labor Day is a “rule” that is broken with very fashionable results, but where did it originate?

Fashion experts say Labor Day probably dates back to the Gilded Age – the same period in the late 19th century when Labor Day was invented. The cool, white dresses that wealthy New Yorkers wore during their summer months in places like Newport, Rhode Island, were packed away at the end of the summer when they returned to the city with its dirty streets.

Christy Crutsinger, a professor of merchandising and digital retail at the University of North Texas, has heard that saying from generations of women in her family. But “that’s not how the fashion world works anymore,” she added.

“People think it, say it, but don’t follow through,” she said.

With the back-to-school shopping rush approaching and many businesspeople moving away from a more casual summer dress code, fashion is a major topic for many people around Labor Day, says Daniel James Cole, adjunct assistant professor of fashion history at the Fashion Institute of Technology and co-author of “The History of Modern Fashion.”

The holiday, he said, “is something like the hinge” between summer clothes and fun and the “return to more serious pursuits.”

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Associated Press writer Wyatte Grantham-Philips contributed to this report.