Ann Arbor is a city in the U.S. state of Michigan and the county seat of Washtenaw County. The 2010 census recorded its population to be 113,934, making it the sixth largest city in Michigan. The city's population was estimated at 117,070 as of July 2015 by the U.S. Census Bureau. The Ann Arbor Metropolitan Statistical Area (MSA) includes all of Washtenaw County, which had a population of 344,791 as of 2010.