In the Nebraska license plate system, Cass County is represented by the prefix 20 (it had the twentieth-largest number of vehicles registered in the county when the license plate system was established in 1922).
1860 - 3,369 1870 - 8,151 1880 - 16,683 1890 - 24,080 1900 - 21,330 1910 - 19,786 1920 - 18,029 1930 - 17,684 1940 - 16,992 1950 - 16,361 1960 - 17,821 1970 - 18,076 1980 - 20,297 1990 - 21,318 2000 - 24,334
As of the census of 2000, there were 24,334 people, 9,161 households, and 6,806 families residing in the county. The population density was 44 people per square mile (17/km²). There were 10,179 housing units at an average density of 18 per square mile (7/km²). The racial makeup of the county was 97.89% White, 0.18% Black or African American, 0.30% Native American, 0.35% Asian, 0.02% Pacific Islander, 0.35% from other races, and 0.92% from two or more races. 1.46% of the population were Hispanic or Latino of any race. 39.4% were of German, 9.6% American, 8.8% Irish and 7.9% English ancestry according to Census 2000.
There were 9,161 households out of which 35.80% had children under the age of 18 living with them, 63.30% were married couples living together, 7.60% had a female householder with no husband present, and 25.70% were non-families. 21.60% of all households were made up of individuals and 9.40% had someone living alone who was 65 years of age or older. The average household size was 2.63 and the average family size was 3.07.
In the county the population was spread out with 27.90% under the age of 18, 7.00% from 18 to 24, 29.00% from 25 to 44, 23.80% from 45 to 64, and 12.30% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 97.70 males. For every 100 females age 18 and over, there were 95.00 males.
The median income for a household in the county was $46,515, and the median income for a family was $52,196. Males had a median income of $36,639 versus $24,612 for females. The per capita income for the county was $20,156. About 4.20% of families and 5.20% of the population were below the poverty line, including 7.10% of those under age 18 and 4.50% of those age 65 or over.