Short answers, pulled from the story.
Twenty and odd enslaved Africans arrived in Virginia in 1619, marking the legal establishment of slavery across all Thirteen Colonies. This event initiated the system that would eventually divide the United States into slave states and free states.
Maine entered the Union as a free state on the 19th of August 1821. It was paired with Missouri's admission as a slave state to maintain Senate balance following the Missouri Compromise of 1820.
President Lincoln issued the Emancipation Proclamation on the 1st of January 1863. The proclamation exempted border states and some occupied territories from immediate freedom while Congress passed the DC Compensated Emancipation Act on the 16th of April 1862.
Delaware Kentucky and New Jersey maintained slavery legally until the 18th of December 1865 when the Thirteenth Amendment took effect. This amendment abolished chattel slavery throughout the United States except as punishment for a crime.