Union County, Ohio

Union County
Union County Courthouse
Location within the U.S. state of Ohio
Ohio's location within the U.S.
Coordinates: 40°19′N 83°22′W / 40.31°N 83.37°W / 40.31; -83.37
Country United States
State Ohio
FoundedApril 1, 1820
Named afterformed from the union of parts of surrounding counties
SeatMarysville
Largest cityMarysville
Area
  Total
437 sq mi (1,130 km2)
  Land432 sq mi (1,120 km2)
  Water5.1 sq mi (13 km2)  1.2%
Population
 (2020)
  Total
62,784
  Density140/sq mi (50/km2)
Time zoneUTC−5 (Eastern)
  Summer (DST)UTC−4 (EDT)
Congressional district4th
Websitewww.unioncountyohio.gov

Union County is a county located in the U.S. state of Ohio. As of the 2020 census, the population was 62,784. Its county seat is Marysville. Its name is reflective of its origins, being the union of portions of Franklin, Delaware, Madison, and Logan counties. Union County is part of the Columbus, Ohio Metropolitan Statistical Area.