The last two states to ratify the Constitution of the United States was Rhode Island and North Carolina. It only took 9 out of the 13 states to approve it, and New Hampshire was the 9th. Rhode Island and North Carolina were the last two out of the 13 to agree.
The Constitution only needed to be ratified by nine of the original thirteen states in order for it to become the law of the land. The last two states that ratified the Constitution were North Carolina, and Rhode Island.