This week’s History Thread falls on two seminal days in American history: the signing of the Constitution in 1787, and the Battle of Antietam seventy-five years later. The former created the document which remains, with a number of amendments, the basis for American law and government, ensuring that the fragile collection of states which had existed before became a strong, powerful nation. The latter, the “bloodiest single day” in American history, was a military stalemate with remarkable consequences: Robert E. Lee’s first invasion of the North failed, George McClellan was finally sacked from the Army of the Potomac, and Lincoln decided to issue his Emancipation Proclamation, turning the war for Union into a war against slavery.