On this day 151 years ago, President Lincoln issued an executive order that proclaimed the freedom of slaves in 10 states — freeing 3.1 million of the 4 million slaves in the U.S. The Emancipation Proclamation was based on the president’s authority as commander in chief of the armed forces. It made the eradication of slavery a goal of the war.

The evening before the order was issued was called Watch Night.  Abolitionists and slaves watched and waited for word that the proclamation had been issued.