Juneteenth is the oldest known celebration of the ending of slavery.
Dating back into 1865, it was on June 19th that the Union Soldiers, led by Major General Gordon Granger, landed at Galveston, TX with news that the war had ended and that all slaves were now free. Note that this was two and a half years after The Emancipation Proclaiming had little impact on the Texans due to minimal number of Union troops to enforce the new Executive order. However, with the surrender of General Lee in April of 1865, and the arrival of General Granger’s regiment, the forces were finally strong enough to influence and overcome the resistance.
Today, the Twin Cities Juneteenth Celebration, founded 30 years ago, is said to be one of the two largest Juneteenth Celebrations in the United States, surpassing even the Texas Celebrations where Juneteenth is a state holiday.