Detroit had a population of 639,111 at the 2020 census, making it the 29th-most populous city in the United States. city on the United States–Canada border, and the seat of government of Wayne County. Young International Airportĭetroit Department of Transportation, Detroit People Mover, QLineĭetroit ( / d ɪ ˈ t r ɔɪ t/ dih- TROYT, locally also / ˈ d iː t r ɔɪ t/) is the most populous city in the U.S.