Though President Lincoln’s Emancipation Proclamation freed slaves in 1863, it was not until June 19, 1865, that Union Maj. Gen. Gordon Granger rode into Galveston, Texas, and found 250,000 blacks still enslaved. He read the proclamation aloud and with his regiment enforced the order for freedom. (source)
Juneteenth, ladies and gentlemen. The end of slavery in America. To paraphrase the Firesign Theatre, our most important national holiday that is not a national holiday.