In some countries, it's a public holiday honoring labor, but in the U.S., activists will use the day as a call to action against President Trump's policies.

Chicago was one of hundreds of cities across the country where people took to the streets to mark May Day, a holiday with deep roots in the city’s labor history.

By the numbers: In Chicago, the May Day protest, which happens annually to support pro-immigration and labor movements, begins at 11am in Union Park on the near West Side. This year, more than 70,000 protesters are expected nationwide, organizers said.