According to the U.S. Census Bureau, the county has a total area of 399 square miles (1,030 km2), of which 395 square miles (1,020 km2) is land and 4.3 square miles (11 km2) (1.1%) is water. It is the fifth smallest county in Ohio in land area and smallest in total area.
There were 11,126 households out of which 31.90% had children under the age of 18 living with them, 61.90% were married couples living together, 7.70% had a female householder with no husband present, and 26.70% were non-families. 22.90% of all households were made up of individuals and 10.40% had someone living alone who was 65 years of age or older. The average household size was 2.56 and the average family size was 3.00.
In the county, the population was spread out with 25.10% under the age of 18, 7.50% from 18 to 24, 27.50% from 25 to 44, 25.70% from 45 to 64, and 14.20% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 98.00 males. For every 100 females age 18 and over, there were 95.40 males.
The median income for a household in the county was $35,509, and the median income for a family was $41,114. Males had a median income of $31,611 versus $21,285 for females. The per capita income for the county was $16,701. About 8.50% of families and 11.40% of the population were below the poverty line, including 17.20% of those under age 18 and 11.10% of those age 65 or over.
As of the 2010 United States Census, there were 28,836 people, 11,385 households, and 8,067 families residing in the county. The population density was 73.1 inhabitants per square mile (28.2/km2). There were 13,698 housing units at an average density of 34.7 per square mile (13.4/km2). The racial makeup of the county was 97.8% white, 0.5% black or African American, 0.3% American Indian, 0.2% Asian, 0.2% from other races, and 1.1% from two or more races. Those of Hispanic or Latino origin made up 0.8% of the population. In terms of ancestry, 29.2% were German, 14.4% were Irish, 11.3% were American, 9.8% were English, and 6.1% were Italian.
Of the 11,385 households, 29.8% had children under the age of 18 living with them, 57.4% were married couples living together, 8.8% had a female householder with no husband present, 29.1% were non-families, and 24.3% of all households were made up of individuals. The average household size was 2.50 and the average family size was 2.95. The median age was 43.1 years.
The median income for a household in the county was $43,148 and the median income for a family was $51,700. Males had a median income of $42,481 versus $26,587 for females. The per capita income for the county was $21,575. About 9.0% of families and 12.6% of the population were below the poverty line, including 18.7% of those under age 18 and 7.1% of those age 65 or over.
The Great Trail Festival, a festival of old fashioned music, arts and crafts, is held near the village of Malvern each year at the end of August and the beginning of September. A celebration of Ohio's colonial history, the event focuses particularly on the region's Native American and French heritage, complete with a small herd of buffalo and battle reenactment.
The Algonquin Mill Fest is another local festival. Held 4 miles south of Carrollton on SR 332 at the Algonquin Mill - a pioneer village with one room schoolhouse, steam-powered saw and flour mills, as well as several other historic buildings. Hand made arts and crafts are sold, along with flour milled during the festival, a pancake breakfast and chicken barbecue dinners.
Flight Fest in Malvern Ohio. This is remote control Airplane competition.