51st state

"51st state" is a phrase used in the United States to refer to the idea of adding an additional state to the current 50-state nation. Proposals for a 51st state may include granting statehood to one of the U.S. territories or Washington, D.C., splitting an existing state, or annexing part or all of a sovereign country. The U.S. has not admitted any new states to the union since 1959, when both Alaska (on January 3) and Hawaii (on August 21) were admitted. Before that, no states had been admitted since Arizona in February 1912. Before Alaska and Hawaii became U.S. states, the equivalent expression was "the 49th state". For example, the National Movement for the Establishment of a 49th State was a 1930s movement that sought to create a primarily Black state in the Southern United States.

In the 2000s, 2010s, and the 2020s, the term has been used most often in reference to active statehood movements in Washington, D.C., and in Puerto Rico, both voted for statehood in recent referendums: D.C. in 2016 and Puerto Rico in 2020. Their admission to the Union as states would require congressional approval. The two regions have different statuses within the U.S., with Puerto Rico as one of the five permanently inhabited U.S. territories, while D.C. has unique status as a federal administrative district. The path to statehood for Puerto Rico in particular would have parallels to the admission process of most U.S. states outside of the original Thirteen British Colonies, which started as territories before becoming states.