Following the bloodiest single day of fighting during the war at the Battle of Antietam, President Lincoln issued the preliminary Emancipation Proclamation on September 22. The proclamation called on rebel states to rejoin the Union by January 1 or have their slaves freed.
Image: Headquarters flag of General Winfield Scott Featherston of Holly Springs who served as a brigade commander at the Battle of Antietam. He later fought in the Battle of Franklin, in 1864, where this flag was captured.