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Mercer County, Ohio facts for kids

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Mercer County
Mercer County courthouse
Mercer County courthouse
Official seal of Mercer County
Map of Ohio highlighting Mercer County
Location within the U.S. state of Ohio
Map of the United States highlighting Ohio
Ohio's location within the U.S.
Coordinates: Lua error in Module:Coordinates at line 610: attempt to index field 'wikibase' (a nil value).
Country  United States
State  Ohio
Founded January 2, 1824
Named for Hugh Mercer
Seat Celina
Largest city Celina
 • Total 473 sq mi (1,230 km2)
 • Land 462 sq mi (1,200 km2)
 • Water 11 sq mi (30 km2)  2.3%%
 • Total 42,528
 • Density 89.91/sq mi (34.71/km2)
Time zone UTC−5 (Eastern)
 • Summer (DST) UTC−4 (EDT)
Congressional districts 4th, 5th, 8th
Grand Lake St. Marys State Park
Graftonoceras fossil nautiloid (Lockport Dolomite, Middle Silurian; Coldwater, southern Mercer County, western Ohio, USA) (15054984258)
Graftonoceras fossil nautiloid, found near Coldwater, southern Mercer County.

Mercer County is located in the U.S. state of Ohio. As of the 2020 census, the population was 42,528. Its county seat is Celina. The county was created in 1820 and later organized in 1824. It is named for Hugh Mercer, an officer in the American Revolutionary War.

Mercer County comprises the Celina, Ohio Micropolitan Statistical Area


Mercer County was founded in 1820 which set it apart from Darke County. Land south of the Greenville Treaty Line was still part of Darke County. An act establishing Mercer County took place on January 2, 1824. In 1837 Van Wert County was detached and the county line established is the current northern border of Mercer County. In 1839 Celina was established as the capital of Mercer County, St. Marys, Ohio was the previous capital. In 1848 the area south of the Greenville Treaty Line to the current southern county line, was attached. When Auglaize County, Ohio was formed, Mercer County's eastern border was moved 6 miles west with the exception of the area south of the Greenville Treaty line. This created the sharp point at Mercer County's south-east corner and was the last county line modification.

In the mid to late 1800s Mercer county became home to many German immigrants, most of whom became farmers in the new world. Many of these German immigrants migrated from northwestern Germany.


According to the U.S. Census Bureau, the county has a total area of 473 square miles (1,230 km2), of which 462 square miles (1,200 km2) is land and 11 square miles (28 km2) (2.3%) is water. The entire county has an elevation difference of less than 300 feet. The highest point is on the southern county line at 1071 feet above sea level. This is in proximity to the head waters for the Wabash River. The lowest point in the county is 780 feet above sea level. This point is located on the northern county line where the St. Marys River crosses over.

Drainage basins

Mercer County has two rivers running through it; the Wabash and the St. Marys. The Wabash watershed is part of the Gulf of Mexico's watershed. The St. Marys watershed is part of Lake Erie's watershed. Creeks between these two watersheds are within a mile of each other at some places in Mercer County. This area/line that divides the drainage basins is known as the St. Lawrence Continental Divide

Beaver Creek

Beaver Creek is the longest and largest creek in Mercer County. It stretches 19.7 miles and has two sections. The first section begins in southern farmland in the county and flows through the town of Montezuma, Ohio and into Grand Lake St. Marys. The other section of the creek begins as a spillway and empties into the Wabash River. Beaver Creek was originally one piece, but was split into two sections after the construction of Grand Lake. The creeks' spillway, and last section, has been the subject of controversy and multimillion-dollar lawsuits. Farmers along Beaver Creek claim their land floods because of the spillway that was put up in 1997, replacing the previous spillway, built in 1913.

See also: Grand Lake St. Marys State Park

Adjacent counties


Historical population
Census Pop.
1820 95
1830 1,110 1,068.4%
1840 8,277 645.7%
1850 7,712 −6.8%
1860 14,104 82.9%
1870 17,254 22.3%
1880 21,808 26.4%
1890 27,220 24.8%
1900 28,021 2.9%
1910 27,536 −1.7%
1920 26,872 −2.4%
1930 25,096 −6.6%
1940 26,256 4.6%
1950 28,311 7.8%
1960 32,559 15.0%
1970 35,265 8.3%
1980 38,334 8.7%
1990 39,443 2.9%
2000 40,924 3.8%
2010 40,814 −0.3%
2020 42,528 4.2%
U.S. Decennial Census
1790-1960 1900-1990
1990-2000 2020

2010 census

As of the 2010 United States Census, there were 40,814 people, 15,532 households, and 11,172 families living in the county. The population density was 88.3 inhabitants per square mile (34.1/km2). There were 17,633 housing units at an average density of 38.1 per square mile (14.7/km2). The racial makeup of the county was 97.4% white, 0.4% Asian, 0.2% Pacific islander, 0.2% American Indian, 0.2% black or African American, 0.6% from other races, and 0.9% from two or more races. Those of Hispanic or Latino origin made up 1.5% of the population. In terms of ancestry, 58.7% were German, 8.8% were American, 8.3% were Irish, and 6.2% were English.

Of the 15,532 households, 32.6% had children under the age of 18 living with them, 60.1% were married couples living together, 7.6% had a female householder with no husband present, 28.1% were non-families, and 24.5% of all households were made up of individuals. The average household size was 2.60 and the average family size was 3.11. The median age was 39.4 years.

The median income for a household in the county was $49,719 and the median income for a family was $60,215. Males had a median income of $42,441 versus $31,069 for females. The per capita income for the county was $22,348. About 6.3% of families and 8.3% of the population were below the poverty line, including 8.9% of those under age 18 and 7.7% of those age 65 or over.






  • Black Creek
  • Butler
  • Center
  • Dublin
  • Franklin
  • Gibson
  • Granville
  • Hopewell
  • Jefferson
  • Liberty
  • Marion
  • Recovery
  • Union
  • Washington
  • Wayne (defunct, now part of Celina)

Unincorporated communities

  • Burrville (defunct)
  • Carthagena
  • Cassella
  • Chattanooga
  • Cranberry Prairie
  • Durbin (Named after George Patrick Durbin)
  • Erastus
  • Ferner (defunct)
  • Hinton (Oregon & Erastus-Durbin intersection)
  • Macedon
  • Maria Stein
  • Mercer
  • Monterey (defunct)
  • Neptune
  • Oregon (defunct)
  • Padua
  • Philothea
  • Sebastian
  • Sharpsburg
  • Scudder (Skeels & Wabash intersection, now defunct)
  • Shively
  • Skeels Crossroads aka Skeels Crossing
  • St. Joseph
  • St. Peter
  • St. Rose
  • Tama (Tamah)
  • Wabash
  • Wendelin

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