President Joe Biden signed the Juneteenth National Independence Day Act into law today as the first new federal holiday in nearly four decades. He described the signing as one of the “greatest honors” of his presidency, according to CNN.

June 19 commemorates the end of slavery in the U.S., marking the 1865 date when the last enslaved people in Texas were freed under the Emancipation Proclamation issued by President Abraham Lincoln over two and half years prior.

“This is a day, in my view, of profound weight and profound power, a day in which we remember the moral stain, [the] terrible toll that slavery took on the country and continues to take,” President Biden said during the ceremony. “We can’t rest until the promise of equality is fulfilled for every one of us in every corner of this nation. That to me is the meaning of Juneteenth.”

Vice President Kamala Harris also spoke at the White House, noting the significance of the surroundings, according to USA Today. “We are gathered here in a house built by enslaved people,” she said.

The senate unanimously passed the bill earlier this week and the House approved it on Wednesday by a vote of 415 to 14. Spearheading the legislation were Sens. Ed Markey, D-Mass., Tina Smith, D-Minn., Cory Booker, D-N.J., John Cornyn, R-Texas, and Rep. Sheila Jackson Lee, D-Texas.

The law takes effect immediately. The U.S. Office of Personnel Management announced that most federal employees will observe the holiday on Friday, since June 19 falls on a Saturday this year.