Hmmm... with all due respect, David, that seemed like the press release version! The real story of Juneteenth is this ....
On June 19, 1865, two-and-a-half years after the signing of the Emancipation Proclamation went into effect (Jan. 1, 1963), a ship sailed into the harbor at Galveston, TX, and a proclamation was read letting the slaves in Texas know that they had been freed! There was partying and rejoicing, as Texas slaves were indeed the last to know.
Since then, black people in Texas have continued to celebrate this day as an "independence day" of sorts, and due to the fact that many Texans have left and spread out all over the country, it still continues to be a day of celebration in many other states, where ex-Texans have carried on the tradition!
I still haven't quite figured out why other people would celebrate it or how it has become such a big event outside of Texas. I think it may be because it's a truely Black thing, something like Kwaanza, that doesn't have any roots in European culture and something Black folks can truly call their own! Then again, I could be wrong!