In the Nebraska license plate system, Hamilton County is represented by the prefix 28 (it had the twenty-eighth-largest number of vehicles registered in the county when the license plate system was established in 1922).
1870 - 130 1880 - 8,267 1890 - 14,096 1900 - 13,330 1910 - 13,459 1920 - 13,237 1930 - 12,159 1940 - 9,982 1950 - 8,778 1960 - 8,714 1970 - 8,867 1980 - 9,301 1990 - 8,862 2000 - 9,403
As of the census of 2000, there were 9,403 people, 3,503 households, and 2,676 families residing in the county. The population density was 17 people per square mile (7/km²). There were 3,850 housing units at an average density of 7 per square mile (3/km²). The racial makeup of the county was 98.43% White, 0.18% Black or African American, 0.12% Native American, 0.22% Asian, 0.49% from other races, and 0.56% from two or more races. 1.14% of the population were Hispanic or Latino of any race.
There were 3,503 households out of which 37.30% had children under the age of 18 living with them, 67.40% were married couples living together, 5.90% had a female householder with no husband present, and 23.60% were non-families. 21.10% of all households were made up of individuals and 10.10% had someone living alone who was 65 years of age or older. The average household size was 2.64 and the average family size was 3.07.
In the county the population was spread out with 29.10% under the age of 18, 5.90% from 18 to 24, 26.50% from 25 to 44, 23.20% from 45 to 64, and 15.30% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 99.40 males. For every 100 females age 18 and over, there were 96.10 males.
The median income for a household in the county was $40,277, and the median income for a family was $45,659. Males had a median income of $29,238 versus $20,308 for females. The per capita income for the county was $17,590. About 5.90% of families and 7.50% of the population were below the poverty line, including 9.80% of those under age 18 and 5.40% of those age 65 or over.