Union County
Also known as Union County, Ohio, Union County, OH
county in Ohio, United States
Key facts
- Country
- United States
- State
- Ohio
- Founded
- April 1, 1820
- Named after
- formed from the union of parts of surrounding counties
- Seat
- Marysville
- Largest city
- Marysville
- Total
- 437 sq mi (1,130 km )
- Land
- 432 sq mi (1,120 km )
- Water
- 5.1 sq mi (13 km ) 1.2%
- Estimate 2025
- 73,446
- Density
- 140/sq mi (54/km )
- Time zone
- UTC−5 ( Eastern )
- Summer dst
Article
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.
History