Boston Mayor Marty Walsh said Thursday he supports establishing Juneteenth as an official holiday, but that the city can’t act without statewide legislation.

“It really has to be a state law,” Walsh said. Adding any holiday to the calendar, he said, would “add to costs to the city, because it’s overtime. We would have to work it into all of the contracts. We wouldn’t be able to do it for tomorrow.”

Juneteenth commemorates June 19, 1865 — the day when enslaved people in Texas found out they were free. As nationwide protests for racial justice have continued in the wake of recent police-killings of black victims, many activists have called for broader recognition of Juneteenth as a reminder of ongoing systemic racism.

“It’s an idea that a lot of people are excited about, as they should be,” Walsh said. “We just have to work through, now, the logistics … of the legislation.”

Boston City Council approved a resolution Wednesday to recognize Juneteenth and several council members say they will offer legislation to make it a holiday.

Meanwhile, Walsh said, “I will be raising the Juneteenth flag at City Hall to honor the history of our black community.”

Even with major Juneteenth events cancelled or curtailed by COVID-19, Walsh encouraged Bostonians of all races to commemorate the day by reflecting on historic and current racism.

“The legacy of injustice and the fight for freedom continue today,” Walsh said. “We’ve come a long way in Boston, but there is so much more work to be done. ... This is a time to make history and move forward.”

After a series of huge protests against police violence in Boston beginning in late May, Walsh announced several steps last week to address the issue, including declaring racism a public health emergency and transferring money out of the police overtime budget into other city programs that support minority communities and other vulnerable populations.