Marshfield is a city in Wood County and Marathon County in the U.S. state of Wisconsin. It is located at the intersection of U.S. Highway 10, Highway 13 and Highway 97. The largest city in Wood County, its population was 19,118 at the 2010 census. Of this, 18,218 were in Wood County, and 900 were in Marathon County. The city is part of the United States Census Bureau's Marshfield-Wisconsin Rapids Micropolitan Statistical Area, which includes all of Wood County (2010 population: 74,749). The portion of the city in Marathon County is part of the Wausau Metropolitan Statistical Area.