The Detroit metropolitan area, often referred to as Metro Detroit, is the metropolitan area located in Southeast Michigan centered on the city of Detroit. As the home of the "Big Three" American automakers (General Motors, Ford, and Chrysler), it is the world's traditional automotive center and a key pillar of the U.S. economy. The city of Detroit is the largest city in the State of Michigan and the 11th largest in the United States.
At its core, Metro Detroit comprises the counties of Wayne, Oakland, and Macomb. These counties are sometimes referred to informally as the Detroit Tri-County Area. The Detroit Urban Area, which serves as the core of the Metropolitan Statistical Area, ranks as the 9th most populous of the United States, with a population of 3,903,377 as of the 2000 census, and area of 1,261.4 square miles (3,267 km2).
The United States Office of Management and Budget defines the Detroit–Warren–Livonia Metropolitan Statistical Area (MSA) as the six counties of Lapeer, Livingston, Macomb, Oakland, St. Clair, and Wayne. As of the 2000 census, the MSA had a population of 4,441,551. The Census Bureau's 2008 estimate placed the population at 4,425,110, which ranks it as the eleventh-largest MSA. The MSA covers an area of 3,913 square miles (10,130 km2).
The nine-county area designated by the United States Census Bureau as the Detroit–Ann Arbor–Flint Combined Statistical Area (CSA) includes the three additional counties of Genesee, Monroe, and Washtenaw, the metropolitan areas of Flint, Ann Arbor, and Monroe, plus the Detroit-Warren-Livonia MSA. It had a population of 5,357,538 as of the 2000 census. The Census Bureau's 2008 estimate placed the population at 5,354,225. This CSA covers an area of 5,814 square miles (15,060 km2). Lenawee County was removed from Detroit's CSA in 2000.
With the adjacent city of Windsor, Ontario and its suburbs, the combined Detroit-Windsor area has a population of about 5.9 million. When the nearby Toledo Metropolitan Area and its commuters are taken into account, the region constitutes a much larger population center. An estimated 46 million people live within a 300-mile (480 km) radius of Detroit proper. Immigration continues to play a role in the region's projected growth with the population of Detroit-Ann Arbor-Flint (CMSA) estimated to be 6,191,000 by 2025.