On June 19, 1965, nearly 2.5 years after the "effective" date of the Emancipation Proclamation, the Union established control over Texas and put the Proclamation into effect -- immediately freeing all Texas slaves and rendering them freedmen.
Although the Emancipation Proclamation was ordered in September 1862 and had an effective date of January 1, 1863, it had no legal effect outside of the Union because it freed only slaves who lived in Confederate states that did not return to the Union by January 1, 1863. In other words, in the seceded states that remained rebellious, it changed nothing. At least not legally. The psychological and political effect was tremendous.
But in Texas, the Confederacy controlled the state and the slaves did not know of their freedom until the Union assumed formal control two months after Gen. Lee surrendered at Appomattox. The Juneteenth celebration was a cultural holiday for a century, is a state holiday here (since 1980), and has become one in 13 other states.