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One Washtenaw
Ann Arbor, Michigan

Washtenaw County
Map of Michigan highlighting Washtenaw County
Located in the state of Michigan
Founded 1826
Seat Ann Arbor
 - Total 722.53 sq mi (1,871 km2)
 - Land 709.94 sq mi (1,839 km2)
 - Water 12.59 sq mi (33 km2), 1.74%
 - (2010) 344,791
 - Density 456/sq mi

Washtenaw County is a county in the U.S. state of Michigan. As of the 2010 census, the population was 344,791. Washtenaw County was officially established as a county in 1826. The county seat is Ann Arbor.  The United States Office of Management and Budget defines the county as part of the Detroit-Warren-Flint Combined Statistical Area. The county is home to the University of Michigan, Eastern Michigan University, Washtenaw Community College, Concordia University Ann Arbor, and the Ann Arbor campus of the Thomas M. Cooley Law School.