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Ann Arbor is a city in the U.S. state of Michigan and the county seat of Washtenaw County. The 2020 census recorded its population to be 123,851, making it the fifth-largest city in Michigan. It is the principal city of the Ann Arbor Metropolitan Statistical Area, which encompasses all of Washtenaw County. Ann Arbor is also included in the larger Greater Detroit Combined Statistical Area.

Ann Arbor is home to the University of Michigan. The university significantly shapes Ann Arbor's economy as it employs about 30,000 workers, including about 12,000 in the medical center. The city's economy is also centered on high technology, with several companies drawn to the area by the university's research and development infrastructure.

Ann Arbor was founded in 1825, named for wives of the village's founders, both named Ann, and the stands of bur oak trees. The University of Michigan moved from Detroit to Ann Arbor in 1837, and the city grew at a rapid rate in the early to mid-20th century. During the 1960s and 1970s, the city gained a reputation as a center for left-wing politics. Ann Arbor became a focal point for political activism, such as opposition to the Vietnam War and support for the legalization of cannabis.