Muskegon County is a county located in the U.S. state of Michigan. As of the 2010 census, the population was 172,188. The county seat is Muskegon.Muskegon County comprises the Muskegon, MI Metropolitan Statistical Area, which is part of the larger Grand Rapids-Wyoming-Muskegon, MI Combined Statistical Area. The White River flows through the county to its mouth at Lake Michigan.