Again being white is not an excuse for ignorant. It is actually a celebration of the last enforcement of the Emancipation Proclamation by a Union Army General Gordon Granger, born in New York, fought at Chickamauga and sent to Texas after the war. This from Wikipedia:
When the war ended, Granger was given command of the
District of Texas.
[10] On June 19, 1865 in the city of
Galveston, one of the first orders of business was to read to the people of Texas Granger's
General Order No. 3 which began with:
[11]
The people of Texas are informed that in accordance with a Proclamation from the Executive of the United States, all slaves are free. This involves an absolute equality of rights and rights of property between former masters and slaves, and the connection therefore existing between them becomes that between employer and free laborer.
This set off joyous demonstrations by freedmen, originating the annual
Juneteenth celebration, which commemorates the abolition of slavery in Texas.