In the Nebraska license plate system, Fillmore County is represented by the prefix 34 (it had the thirty-fourth-largest number of vehicles registered in the county when the license plate system was established in 1922).
1870 - 238 1880 - 10,204 1890 - 16,022 1900 - 15,087 1910 - 14,674 1920 - 13,671 1930 - 12,971 1940 - 11,417 1950 - 9,610 1960 - 9,425 1970 - 8,137 1980 - 7,920 1990 - 7,103 2000 - 6,634
As of the census of 2000, there were 6,634 people, 2,689 households, and 1,801 families residing in the county. The population density was 12 people per square mile (4/km²). There were 2,990 housing units at an average density of 5 per square mile (2/km²). The racial makeup of the county was 97.75% White, 0.21% Black or African American, 0.44% Native American, 0.06% Asian, 0.02% Pacific Islander, 0.83% from other races, and 0.69% from two or more races. 1.66% of the population were Hispanic or Latino of any race. 48.6% were of German, 10.4% Czech, 7.1% Irish and 7.0% English ancestry according to Census 2000.
There were 2,689 households out of which 30.20% had children under the age of 18 living with them, 59.10% were married couples living together, 5.00% had a female householder with no husband present, and 33.00% were non-families. 30.20% of all households were made up of individuals and 16.30% had someone living alone who was 65 years of age or older. The average household size was 2.37 and the average family size was 2.95.
In the county the population was spread out with 26.30% under the age of 18, 5.10% from 18 to 24, 24.00% from 25 to 44, 23.30% from 45 to 64, and 21.30% who were 65 years of age or older. The median age was 41 years. For every 100 females there were 93.50 males. For every 100 females age 18 and over, there were 91.30 males.
The median income for a household in the county was $35,162, and the median income for a family was $41,725. Males had a median income of $29,813 versus $18,507 for females. The per capita income for the county was $17,465. About 4.80% of families and 7.80% of the population were below the poverty line, including 8.20% of those under age 18 and 10.00% of those age 65 or over.