If you are really going to celebrate the end of slavery, the date to celebrate is December 6, not June 19. December 6th, 1865 is the date of the ratification of the Thirteenth Amendment which abolished slavery.
Slavery continued to exist, and was legal, in the four border states (Missouri, Kentucky, Maryland, and Delaware), as well as West Virginia and parts of Louisiana for almost six months after June 19, 1865.
June 19th is only relevant in southern Texas.
Unfortunately the END of Slavery is not what’s at the heart of this happening now.
Slavery was ended in Missouri in January 1865 and in Maryland in October 1864.