Detroit is the most populous city in the state of Michigan in the United States. In 1950, Detroit was the fifth most populous city in the United States, with 1.8 million people. It was the 10th most populous city in the United States at the time of the 2000 census, with 950,000 people. By the 2020 census, Detroit fell to the 27th largest, because people moved away, and it had 640,000 people. Over four million people live in Detroit and its surrounding counties. The city borders Windsor, Ontario in Canada. The international border between Detroit and Windsor is one of the most crossed in the world.