That must be in 1863 that you are talking about...Slaves in confederate states (that weren't already taken over the Union) were freed (Emancipation proclamation)
It was business as usual for states that already took an L to the union... the EP was a war tactic... Nothing more
It wasn't until in 1865 when the 13th amendment came around that slavery was "outlawed"
June 19th is a specific date for Blacks in Texas when some general proclaimed that they were free...
So it is the day that we generally use to commemorate African-American Independence