Juneteenth is officially a federal holiday.

On Thursday, President Joe Biden signed a bill into law commemorating June 19, which marks the true end of slavery in the U.S., as a federal holiday.

"This is a day of profound weight and profound power," Biden said at the signing ceremony, calling it a day to remember "the moral stain" of slavery. As he signed the bill, Opal Lee, who's 94 and has led a decade-long effort to make Juneteenth a holiday, stood by his side on stage. The Texas native was one of the first to get a pen Biden used to sign the legislation.

Vice President Kamala Harris also highlighted the significance of establishing the holiday.

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"National holidays are something important. These are days when we as a nation have decided to take stock and often to acknowledge our history," Harris said. "We must learn from our history, and we must teach our children our history."

"We have come far and we have far to go, but today is a day of celebration," she said.

On June 19, 1865, Union troops arrived in Galveston, Texas to tell the state's enslaved people they were free. This came more than two months after the end of the Civil War, and years after President Abraham Lincoln issued the Emancipation Proclamation (which freed enslaved people on paper, but not right away in practice).

Advocates have been calling for a federal holiday for years, but the turning point in their fight came after last summer's protests against police brutality and racial injustice following the murder of George Floyd.

Juneteenth is now the twelfth federal holiday. The last time the federal government added a new holiday was in 1986 when it recognized Martin Luther King Jr. Day. It had taken 15 years to get Congress to designate Martin Luther King Jr. Day as a federal holiday.

As a national holiday, federal employees will get a paid day off on Juneteenth (or on the Friday or Monday closest to it if June 19 falls on a weekend). So this year, they will get Friday off. Last year, several companies, such as Nike, Target, Twitter, Spotify, TikTok, and Mashable's parent company, J2 Global, designated Juneteenth as a paid company holiday. (Tesla infamously said employees could take the day off, but they wouldn't get paid.) A federal holiday may pave the way for even more private companies to offer a paid holiday on Juneteenth.

Biden's signature comes after the Senate and House of Representatives approved the holiday in quick succession this week. All that was holding the Senate back was one Republican who blocked the holiday's passage last year over cost concerns (it'll cost roughly $600 million a year to give federal employees the paid day off). This week, the senator relented, and then both the Senate and House swiftly and easily approved the holiday.

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While designating Juneteenth as a holiday raises awareness of an important historical moment, Bernice King, CEO of The King Center, a social change nonprofit, and Martin Luther King Jr.'s daughter, said Congress needs to do more than take ceremonial action. She called on lawmakers to pass legislation to prevent police violence and voter suppression.

"There is just so much that has to happen in our Senate to really deliver substance to Black people," she said on CNN before the signing.

Texas was the first state to declare Juneteenth an official state holiday in 1980. Throughout the years, D.C. and 49 states have followed its lead. While it's not a paid holiday in every state that's recognized Juneteenth, at least seven states have designated it a paid holiday for state employees. South Dakota is the only state to not recognize Juneteenth.