Mercer County, Ohio
County seat: Celina · Population 42,737 (2025) · 462 sq mi
Mercer County is the 57th most populous of Ohio's 88 counties, with 42,737 people (2025 estimate). Its county seat is Celina. The map shows its 9 cities and towns and the 6 neighboring counties.
Mercer County facts
- County seat
- Celina
- Population (2025 estimate)
- 42,737 +0.5% since 2020
- Land area
- 462 sq mi 36th largest of 88
- Water area
- 11 sq mi
- Population density
- 92 per sq mi
- Established
- 1820
- Named after
- Hugh Mercer Jacobite and General in the American Revolutionary War
- Largest city
- Celina 10,936
- Median household income
- $76,782
- Cities and towns
- 9 plus 1 CDPs
- ZIP codes
- 18
- Time zone
- Eastern
- FIPS code
- 39107
Cities and towns in Mercer County
Mercer County has 9 incorporated cities, towns and villages. Populations count the people living inside Mercer County; cities that cross a county line also list the other counties.
| Name | Type | Population 2025 | Also in |
|---|---|---|---|
| Celina (county seat) | City | 10,936 | |
| Coldwater | Village | 4,716 | |
| St. Henry | Village | 2,624 | |
| Fort Recovery | Village | 1,476 | |
| Rockford | Village | 1,039 | |
| Mendon | Village | 613 | |
| Chickasaw | Village | 351 | |
| Burkettsville | Village | 202 | Darke County |
| Montezuma | Village | 149 |
Unincorporated communities (CDPs)
Census-designated places are communities without their own city government; the county provides their services.
| Community | Population | Also in |
|---|---|---|
| Maria Stein | 1,305 |
ZIP codes in Mercer County
18 ZIP codes reach into Mercer County. ZIP codes ignore county lines, so some also cover a neighboring county.
- 45310 also Darke County
- 45388 also Darke and Shelby counties
- 45822
- 45826
- 45828
- 45845 also Shelby and Auglaize counties
- 45846 also Darke County
- 45860
- 45862 also Auglaize County
- 45865 also Auglaize and Shelby counties
- 45866
- 45869 also Auglaize and Shelby counties
- 45882 also Van Wert County
- 45883 also Darke County
- 45885 also Auglaize County
- 45887 also Allen, Auglaize and Van Wert counties
- 45894 also Van Wert County
- 45898 also Van Wert County
Population of Mercer County, 2020–2025
Mercer County grew by 208 people (+0.5%) between April 2020 and July 2025: 933 more births than deaths and a net loss of 719 people from migration.
| Year (July 1) | Population |
|---|---|
| 2020 | 42,534 |
| 2021 | 42,366 |
| 2022 | 42,343 |
| 2023 | 42,360 |
| 2024 | 42,520 |
| 2025 | 42,737 |
Neighboring counties
- Auglaize County east · 45,909 people
- Van Wert County north · 29,013 people
- Darke County south · 51,520 people
- Jay County, Indiana west · 20,118 people
- Adams County, Indiana northwest · 36,650 people
- Shelby County southeast · 48,065 people
Printable Mercer 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) (100 KB)
- PNG (2400 px) (80 KB)
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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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