The last two states to ratify the U.S. Constitution were North Carolina and Rhode Island. North Carolina voted to ratify the Constitution in 1789, and Rhode Island followed in 1790.
North Carolina originally balked at voting to ratify the Constitution, but when Congress floated the idea of a bill of rights, North Carolina changed its stance.
Rhode Island originally rejected the Constitution outright in 1788 by a popular referendum; the people of Rhode Island voted against it. However, the state was faced with the possibility of being looked at as a foreign country. With the pressure mounting, the state ratified the Constitution by only two votes during the ratifying convention in 1790.