Rhode Island was the last original state to ratify the U.S. Constitution, doing so on May 29, 1790.
Rhode Island's convention approved ratification by a narrow vote of 34 to 32. The state had resisted joining the constitutional system after the new federal government began operating because many residents feared expanded national power and possible threats to individual liberty. It had also declined to send delegates to the Constitutional Convention in 1787.
The Constitution had already taken effect among the ratifying states after New Hampshire became the ninth to ratify in June 1788. Rhode Island's delayed decision therefore did not prevent the federal government from beginning operations. It did, however, complete the original thirteen-state ratification sequence.
North Carolina was the penultimate original state, ratifying in November 1789. Rhode Island's eventual approval came after political pressure and debate over amendments, including protections later associated with the Bill of Rights. Its late vote is why Rhode Island is often called the last of the original thirteen to enter the constitutional Union.