Adjacent counties

• Huron County (north)
• Ashland County (east)
• Knox County (south)
• Morrow County (southwest)
• Crawford County (west)

2000 census

As of the census^[10] of 2000, there were 128,852 people, 49,534 households, and 34,277 families living in the county. The population density was 259 people per square mile (100 people/km²). There were 53,062 housing units at an average density of 107 units per square mile (41/km²). The racial makeup of the county was 88.16% White, 9.43% Black or African American, 0.20% Native American, 0.51% Asian, 0.03% Pacific Islander, 0.38% from other races, and 1.28% from two or more races. 0.93% of the population were Hispanic or Latino of any race. 96.0% spoke English, 1.2% German and 1.2% Spanish as their first language.

There were 49,534 households, out of which 30.90% had children under the age of 18 living with them, 54.30% were married couples living together, 11.40% had a female householder with no husband present, and 30.80% were non-families. 26.50% of all households were made up of individuals, and 10.90% had someone living alone who was 65 years of age or older. The average household size was 2.47 and the average family size was 2.98.

In the county, the population was spread out, with 24.80% under the age of 18, 8.40% from 18 to 24, 28.60% from 25 to 44, 24.10% from 45 to 64, and 14.20% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 101.30 males. For every 100 females age 18 and over, there were 99.30 males.

The median income for a household in the county was $37,397, and the median income for a family was $45,036. Males had a median income of $35,425 versus $22,859 for females. The per capita income for the county was $18,582. About 8.20% of families and 10.60% of the population were below the poverty line, including 15.30% of those under age 18 and 7.70% of those age 65 or over.

2010 census

As of the 2010 United States Census, there were 124,475 people, 48,921 households, and 32,510 families living in the county.^[11] The population density was 251.3 inhabitants per square mile (97.0/km²). There were 54,599 housing units at an average density of 110.2 units per square mile (42.5 units/km²).^[12] The racial makeup of the county was 87.5% white, 9.4% black or African American, 0.6% Asian, 0.2% American Indian, 0.4% from other races, and 1.9% from two or more races. Those of Hispanic or Latino origin made up 1.4% of the population.^[11] In terms of ancestry, 30.6% were German, 13.3% were Irish, 12.6% were English, and 8.0% were American.^[13]

Of the 48,921 households, 29.9% had children under the age of 18 living with them, 49.7% were married couples living together, 12.5% had a female householder with no husband present, 33.5% were non-families, and 28.8% of all households were made up of individuals. The average household size was 2.40 and the average family size was 2.93. The median age was 40.9 years.^[11]

The median income for a household in the county was $42,664 and the median income for a family was $54,637. Males had a median income of $42,919 versus $31,228 for females. The per capita income for the county was $21,459. About 8.6% of families and 12.4% of the population were below the poverty line, including 18.9% of those under age 18 and 8.2% of those age 65 or over.^[14]

County officials

• Commissioners: Cliff Mears, Darrell Banks, Tony Vero
• Prosecutor: Jodie Schumacher
• Sheriff: J. Steve Sheldon
• Auditor: Patrick W. Dropsey
• Treasurer: Bart Hamilton
• Recorder: Sarah Davis
• Clerk of Courts: Linda H. Frary
• Engineer: Adam Gove
• Judges of the Court of Common Pleas: Phillip Naumoff and Brent Robinson
• Judges of the Domestic Relations Court: Beth Owens
• Judges of the Juvenile Court: (William) Steven McKinley
• Judges of the Probate Court: Kelly Badnell

Cities

• Galion (part)
• Mansfield (county seat)
• Ontario
• Shelby

Villages

• Bellville
• Butler
• Crestline (part)
• Lexington
• Lucas
• Plymouth (part)
• Shiloh

Townships

Census-designated places

• Lincoln Heights
• Roseland

Unincorporated communities

• Bangorville
• Olivesburg

Ghost towns

• Newville
• Winchester