The longest river in the United States (8)

I believe the answer is:

missouri

(Other definitions for missouri that I've seen before include "Midwestern US state" , "US state, capital Jefferson City" , "24th American state to join the Union, 1821" , "American state's" , "Biggest tributary of the Mississippi" .)

I've seen this clue in The Guardian.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.