On Thursday, President Joe Biden signed a bill marking Juneteenth as a federal holiday into law. That makes Juneteenth the nation’s first new federal holiday in decades. *** Juneteenth marks the day when Union soldiers arrived in Galveston, Texas, on June 19, 1865 — 2½ years after the Emancipation Proclamation and two months after the end of the Civil War — and announced to enslaved Black people that they were free. *** @amnaonpbs explores the significance of the holiday with Harvard history, ra