Their aim was to show support for all the workers currently off the job during what's being called a "hot labor summer."
"The power of organized labor when they do get collectively together," said Tim Henson of Sheet Metal Workers' International Association Local 105. "It shows we're still here, that we haven't gone away."
The theme of the 44th annual Los Angeles/Long Beach Harbor Labor Coalition Labor Day Parade & Picnic Rally was "Union Labor Built the American Dream."
"All unions are tied together," said Shomari Davis of the International Brotherhood of Electrical Workers. "Our values overlap, and if all workers are strong then we can all work together to make sure America is better. We are partners with our contractors but we understand SAG-AFTRA and the writers, they need to have more of a partnership with the producers. So that's why we support them."
Davis was referring to the Screen Actors Guild and American Federation of Television and Radio Artists, and the Writers Guild of America, both of whose members are on strike.
But it's not just SAG-AFTRA and the WGA -- hotel workers have also been on strike. And Los Angeles city workers took part in a 24-hour strike.
SAG-AFTRA requests approval to strike against video game companies
In Wilmington, the Labor Day holiday brought not just unions but also marching bands and community groups together to honor workers and their families.
"The people build America," said David Garcia of the Sheet Metal Workers' International Association. "The people build bridges and buildings, cars, roads, homes."
Tim Henson said Labor Day is about celebrating the work of his union, sheet-metal workers, their skills, their value to society -- and sending the message that unions of all types, united together, help everyone.
"My dad became a sheet metal worker sometime in the '70s and it was life-changing for my family, Henseon said. "And now it's continued on, where my daughter is actually a sheet-metal worker now."