May 29

Rhode Island may have been the first of the United States to outlaw slavery but it was the last of them to ratify the Constitution and became the last of the original 13 colonies to join the United States. It didn’t do that until the 29th in 1790.
I know that the USA didn’t exist until 1776. I also know that I’m pushing it here. On May 18, 1652, the governing body of the area that was destined to be Rhode Island passed a law abolishing slavery.