Wednesday marks the third annual observance in the United States of Juneteenth, a federal holiday that commemorates the 1865 emancipation of enslaved Black people at the end of the Civil War.

The holiday’s name stems from June 19th, 1865, when U.S. Army Major General Gordon Granger marched into Galveston, Texas, and informed an estimated 250,000 slaves they were free after four years of war between the victorious Union army of the U.S. north and the southern Confederate states.

Granger’s order enforced the Emancipation Proclamation signed on January 1, 1863, by then-President Abraham Lincoln that freed more than 3 million enslaved Blacks throughout the Confederacy but did not truly take effect until the end of the war when the Confederacy surrendered.

Black communities commemorated the date as the actual end of slavery in private celebrations throughout the following century. The first official observance of Juneteenth came in 1980, when Texas declared it a state holiday. Other communities across the U.S. slowly began to adopt the annual observance as a public holiday, eventually leading to all 50 states and the District of Columbia now recognizing the day in some form.

The drive to make Juneteenth a federal holiday gained momentum during the Black Lives Matter movement against racism and police brutality, especially after the murder of African American George Floyd by a white Minneapolis police officer in 2020.

Much of the success in galvanizing support for a national holiday is credited to Opal Lee, a retired African American teacher and activist known as “the grandmother of Juneteenth.” As a child, Lee witnessed a group of 500 white supremacists vandalize and burn her family’s home to the ground.

In 2016, at the age 89, she began a walking campaign, traveling hundreds of kilometers from her hometown of Fort Worth, Texas, to Washington, D.C., to press for a Juneteenth federal holiday.

Her efforts became a reality in 2021, when President Joe Biden signed legislation passed by Congress marking Juneteenth as the 11th nationally recognized holiday.

In a proclamation recognizing this Juneteenth as “a day of observance,” President Biden said Juneteenth “not only marks the end of America’s original sin of slavery but also the beginning of the work at the heart and soul of our Nation: Making the promise of America real for every American.”