Although President Lincoln's Emancipation Proclamation was issued on January 1, 1863, it was not until June 19, 1865 that Union forces under the command of General Gordon Granger arrived to enforce the abolition of slavery in the state of Texas.  That day is commemorated annually as "Juneteenth," a combination of the words "June" and "19^th" and is celebrated as an official holiday in Texas and thirteen other states.

Bonus Question:
Which was the last Confederate state to be readmitted to the Union?
Answer:  Georgia, on July 15, 1870