Union County, Ohio
County seat: Marysville · Population 73,446 (2025) · 432 sq mi
Union County is the 34th most populous of Ohio's 88 counties, with 73,446 people (2025 estimate). Its county seat is Marysville. The map shows its 7 cities and towns and the 7 neighboring counties.
Union County facts
- County seat
- Marysville
- Population (2025 estimate)
- 73,446 +17% since 2020
- Land area
- 432 sq mi 45th largest of 88
- Water area
- 5 sq mi
- Population density
- 170 per sq mi
- Established
- 1820
- Largest city
- Marysville 30,190
- Median household income
- $112,322
- Cities and towns
- 7 plus 2 CDPs
- ZIP codes
- 21
- Time zone
- Eastern
- FIPS code
- 39159
Cities and towns in Union County
Union County has 7 incorporated cities, towns and villages. Populations count the people living inside Union County; cities that cross a county line also list the other counties.
| Name | Type | Population 2025 | Also in |
|---|---|---|---|
| Marysville (county seat) | City | 30,190 | |
| Dublin | City | 4,265 | Delaware and Franklin counties |
| Richwood | Village | 2,640 | |
| Milford Center | Village | 959 | |
| Plain City | Village | 730 | Madison County |
| Magnetic Springs | Village | 316 | |
| Unionville Center | Village | 235 |
Unincorporated communities (CDPs)
Census-designated places are communities without their own city government; the county provides their services.
| Community | Population | Also in |
|---|---|---|
| New California | 1,672 | |
| Raymond | 415 |
ZIP codes in Union County
21 ZIP codes reach into Union County. ZIP codes ignore county lines, so some also cover a neighboring county.
- 43007
- 43015 also Delaware County
- 43016 also Franklin and Delaware counties
- 43017 also Franklin and Delaware counties
- 43029 also Madison County
- 43036
- 43040 also Delaware County
- 43045 also Champaign County
- 43060 also Champaign and Logan counties
- 43061 also Delaware County
- 43064 also Madison and Franklin counties
- 43067 also Logan County
- 43077
- 43084 also Champaign County
- 43302 also Marion and Crawford counties
- 43319 also Logan County
- 43340 also Hardin County
- 43342 also Marion and Delaware counties
- 43344 also Delaware and Marion counties
- 43345 also Logan and Hardin counties
- 43358 also Logan County
Population of Union County, 2020–2025
Union County grew by 10,651 people (+17%) between April 2020 and July 2025: 1,405 more births than deaths and a net gain of 9,228 people from migration.
| Year (July 1) | Population |
|---|---|
| 2020 | 63,069 |
| 2021 | 65,101 |
| 2022 | 66,942 |
| 2023 | 69,830 |
| 2024 | 71,983 |
| 2025 | 73,446 |
Neighboring counties
- Delaware County east · 242,032 people
- Logan County west · 46,302 people
- Madison County south · 46,985 people
- Marion County northeast · 65,115 people
- Champaign County southwest · 38,820 people
- Hardin County northwest · 30,072 people
- Franklin County southeast · 1,361,536 people
Printable Union County map
The PDF is a vector file with real text: it prints sharp on Letter paper and you can search it for a town. The PNG is 2400 pixels wide for slides and documents. Both are free to use with a credit to WhichCounty.
- PDF (Letter) (99 KB)
- PNG (2400 px) (82 KB)
Paste this code to embed the map on your site:
Sources
- Boundaries: U.S. Census Bureau, 2025 Cartographic Boundary Files (1:500,000).
- Population: Census Bureau county and city estimates, Vintage 2025. CDP populations: American Community Survey 2020–2024.
- Places and ZIP codes: Census Bureau 2026 Gazetteer and 2020 ZIP Code Tabulation Area relationship files.
- County seat, founding year and name origin: Wikidata (CC0), checked against state sources.
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