what was the last state to become a state
Making the world better, one answer at a time.   The last four states to join the US were New Mexico, Arizona, Alaska and Hawai'i.   New Mexico and Arizona joined in 1912.   Alaska joined on January 3, 1959.
In 1959, the United States added two more states to the Union: Alaska and Hawaii, the non-contiguous states. Alaska was admitted to the Union on January 3, 1959, becoming the 49th state, and Hawaii joined on August 21, 1959, becoming the 50th state.