Mercer County Map, Ohio

Written and Fact-checked by | Updated On: April 30, 2026 | 13:31 ET

Map of Mercer County - Mercer County is a county located in the U.S. state of Ohio. Mercer County Map showing cities, highways, important places and water bodies. Get Where is Mercer County located in the map, major cities in Mercer county, population, areas, and places of interest.

Map of Mercer County, Ohio

Map of Mercer County, Ohio

About Mercer County Map, Ohio: The map showing the county boundary, county seat, major cities, highways, water bodies and neighbouring counties.

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About Mercer County, Ohio

Mercer County is a county located in the U.S. state of Ohio. It's county seat is Celina. As per 2020 census, the population of Mercer County is 42309 people and population density is square miles. According to the United States Census Bureau, the county has a total area of 463.27 sq mi (1,200 km2). Mercer County was established on -29127.

Mercer County Facts

ContinentNorth America
CountryUnited States
StateOhio
County SeatCelina
Largest City/TownCelina
EstablishedApril 1, 1820
Total Area469 sq mi (1,215 sq km)
Land Area462 sq mi (1,197 sq km)
Water Area7.5 sq mi (19.4 sq km)
Population42,528 (Census 2020)
Population Density92 people per sq mi
Time ZoneEastern Time Zone (ET)
Major HighwaysUS-127, State Route 29, State Route 49, State Route 118, State Route 219
Neighboring CountiesDarke County, Auglaize County, Van Wert County, Jay County (IN), Adams County (IN)
Famous ForGrand Lake St. Marys, agriculture, boating and fishing
Top AttractionsGrand Lake St. Marys State Park, Celina Lakefront, Mercer County Fairgrounds, Coldwater Historic District
Official Websitehttps://www.mercercountyohio.org/

Cities and Towns in Mercer County, Ohio

  • Celina (county seat) – 10,935 (Census 2020)
  • Coldwater – 4,774 (Census 2020)
  • St. Henry – 2,822 (Census 2020)
  • Rockford – 1,051 (Census 2020)

Roads and Highways in Mercer County, Ohio

Mercer County is connected by highways that link it to western Ohio and eastern Indiana.

  • US-127 – major north-south route connecting Celina to Van Wert and Greenville
  • State Route 29 – east-west highway linking Celina to Sidney and Decatur, Indiana
  • State Route 49 – runs north-south connecting the county to Darke County and Indiana
  • State Route 118 – links Celina to St. Marys and surrounding communities
  • State Route 219 – connects Celina to Coldwater and eastern areas

Neighboring Counties of Mercer County

  • Van Wert County (north)
  • Auglaize County (east)
  • Darke County (south)
  • Jay County, Indiana (west)
  • Adams County, Indiana (northwest)

Top Attractions in Mercer County, Ohio

Mercer County is known for its lakeside recreation, small towns, and outdoor activities.

  • Grand Lake St. Marys State Park – popular for boating, fishing, and camping
  • Celina Lakefront – scenic area with parks, walking paths, and events
  • Coldwater Historic District – charming area with local shops and heritage
  • Mercer County Fairgrounds – hosts one of Ohio’s largest county fairs
  • St. Henry Community Park – local park with recreational facilities
  • Windy Point Park – lakeside park with camping and picnicking
  • Shanes Park – community park with sports fields and green space
  • Lake Improvement Association areas – scenic spots around Grand Lake

Distance from Mercer County to Nearby Cities

  • Mercer County to Lima – 35 mi (56 km)
  • Mercer County to Dayton – 75 mi (121 km)
  • Mercer County to Fort Wayne – 50 mi (80 km)
  • Mercer County to Columbus – 110 mi (177 km)
  • Mercer County to Toledo – 110 mi (177 km)

FAQs about Mercer County

Where is Mercer County located?

Mercer County is located in western Ohio along the Indiana border.

What is Mercer County known for?

It is known for Grand Lake St. Marys, agriculture, and outdoor recreation.

What is the population of Mercer County?

The population was 42,528 according to the 2020 Census.

What is the county seat of Mercer County?

The county seat is Celina.

Are there attractions in Mercer County?

Yes, the county offers lakes, parks, and community events.