Founded in Apr 1, 1820, Union County is one of 88 counties in the state of Ohio. Historically, Union County was formed from Delaware, Franklin, Logan, and Madison Counties. The city of Marysville is the county seat. With FIPS code of 159, Union County has a population of 64,971 and area of 436.65 square miles (1,131 km2).
List of all cities in Union County, OH alphabetically
| City/Town | Postal Code | Area Code |
| Broadway, OH | 43007 | 937 |
| Irwin, OH | 43029 | 937 |
| Magnetic Springs, OH | 43036 | 937 |
| Marysville, OH | 43040 | 937 |
| 43041 | 937 | |
| Milford Center, OH | 43045 | 937 |
| O M Scott Co, OH | 43041 | 937 |
| Raymond, OH | 43067 | 937 |
| Richwood, OH | 43344 | 740 |
| Unionville Center, OH | 43077 | 740 |