Detroit is a city.
Detroit ( [ dᵻˈtrɔɪt ] ) is the most populous city in the U.S. state of Michigan , the largest city on the United States -- Canada border , and the seat of Wayne County . The municipality of Detroit had a 2015 estimated population of 677,116 , making it the 21st-most populous city in the United States . With expansion of the auto industry in the early 20th century , the city and its suburbs experienced rapid growth , and by the 1940s , the city had become the fourth-largest in the country . In 2013 , Detroit became the largest U.S. city to file for bankruptcy , which it successfully exited in December 2014 , when the city government regained control of Detroit 's finances .