Major highways

• U.S. Highway 20
• U.S. Highway 65
• Iowa Highway 57
• Iowa Highway 175

Adjacent counties

• Franklin County (north)
• Butler County (northeast)
• Grundy County (east)
• Marshall County (southeast)
• Story County (southwest)
• Hamilton County (west)
• Wright County, Iowa (northwest)

2020 census

The 2020 census recorded a population of 16,878 in the county, with a population density of 29.1426/sq mi (11.2520/km²). 95.71% of the population reported being of one race. There were 8,032 housing units, of which 7,070 were occupied.^[1]

2010 census

The 2010 census recorded a population of 17,534 in the county, with a population density of 30.8014/sq mi (11.8925/km²). There were 8,224 housing units, of which 7,296 were occupied.^[13]

2000 census

As of the census^[14] of 2000, there were 18,812 people, 7,628 households, and 5,087 families residing in the county. The population density was 33 people per square mile (13 people/km²). There were 8,318 housing units at an average density of 15 units per square mile (5.8 units/km²). The racial makeup of the county was 97.14% White, 0.62% Black or African American, 0.13% Native American, 0.32% Asian, 0.05% Pacific Islander, 1.24% from other races, and 0.50% from two or more races. 2.42% of the population were Hispanic or Latino of any race.

There were 7,628 households, out of which 29.50% had children under the age of 18 living with them, 57.10% were married couples living together, 6.50% had a female householder with no husband present, and 33.30% were non-families. 29.40% of all households were made up of individuals, and 15.70% had someone living alone who was 65 years of age or older. The average household size was 2.35 and the average family size was 2.91.

In the county, the population was spread out, with 24.70% under the age of 18, 8.40% from 18 to 24, 23.80% from 25 to 44, 22.40% from 45 to 64, and 20.70% who were 65 years of age or older. The median age was 41 years. For every 100 females there were 95.70 males. For every 100 females age 18 and over, there were 90.10 males.

The median income for a household in the county was $35,429, and the median income for a family was $41,891. Males had a median income of $30,515 versus $21,068 for females. The per capita income for the county was $17,537. About 5.50% of families and 8.00% of the population were below the poverty line, including 9.90% of those under age 18 and 6.20% of those age 65 or over.

Cities

Census-designated place

• Garden City

Other unincorporated communities

• Cleves
• Gifford

Townships

Population ranking

The population ranking of the following table is based on the 2020 census of Hardin County.^[1]

† county seat