For the African American community, June 19 marks the annual observance of an important holiday: Juneteenth. Many teachers are aware of the significance of this event, and, if school for them is still in session, they may be planning an observance of the occasion with their students.

Juneteenth marks the 1865 arrival of Federal troops under the command of US General Gordon Granger in Galveston, Texas. Their military mission was to take control of the state following the Civil War, and to ensure that all enslaved people living there had been freed. Until that day, 250,000 enslaved people in Texas were unaware that slavery had been declared officially ended. The troops’ arrival came a full two and a half years after the signing of the Emancipation Proclamation.

The year following Granger’s arrival, freedmen in Texas organized the first of what became the annual celebration of “Jubilee Day” on June 19. In the decades since, Juneteenth commemorations featured music, barbecues, prayer services, and other holiday activities. As Black people migrated from Texas to other parts of the country, the tradition of celebrating Juneteenth spread.

Juneteenth is considered the longest-running African American holiday in US history. In 1979, Texas became the first state to declare Juneteenth an official holiday. Efforts to make the celebration a national holiday have, so far, stalled in Congress, but as of this year, 47 states recognize Juneteenth as a state holiday.