June 19 has been known as "Juneteenth Day," a combination of “June” and “nineteenth” which is the oldest celebration of the end of slavery in the United States. It is also known as African American Freedom Day or Emancipation Day.
Although President Lincoln freed the slaves in the Emancipation Proclamation of Jan. 1, 1863, the good news didn't reach the folks in Galveston, Texas, until June 19, 1865 when Major General Gordon Granger and his troops arrived there, announcing the end of the Civil War.
Below is an excerpt from Granger’s speech:
“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 heretofore existing between them becomes that between employer and free laborer."
The Civil Rights era saw a resurgence of observation of the day, and it's been a staple of Milwaukee festivals since the 1970s.