who was the last of the 13 states to ratify the constitution?

The last of the original 13 states to ratify the U.S. Constitution was Rhode Island , on May 29, 1790.

Rhode Island held out for years due to deep worries about a stronger central government, taxation, and protection of individual and state rights, earning the nickname “Rogue Island” for its resistance. It finally agreed to ratification after the new federal system was already in operation and after the Bill of Rights—promising protections like freedom of speech and religion—was moving forward, which eased many of its concerns.