Gage County lies on the south line of Nebraska. Its south boundary line abuts the north boundary line of the state of Kansas. The Big Blue River runs SSE through the central part of the county. According to the US Census Bureau, the county has a total area of, of which is land and is water.
As of the 2000 United States Census, there were 22,993 people, 9,316 households, and 6,204 families in the county. The population density was 27 people per square mile. There were 10,030 housing units at an average density of 12 per square mile. The racial makeup of the county was 97.69% White, 0.32% Black or African American, 0.58% Native American, 0.28% Asian, 0.03% Pacific Islander, 0.26% from other races, and 0.84% from two or more races. 0.85% of the population were Hispanic or Latino of any race. 56.6% were of German, 6.9% Irish, 6.3% English and 6.3% American ancestry. There were 9,316 households out of which 30.30% had children under the age of 18 living with them, 56.70% were married couplesliving together, 7.10% had a female householder with no husband present, and 33.40% were non-families. 29.20% of all households were made up of individuals and 15.00% had someone living alone who was 65 years of age or older. The average household size was 2.36 and the average family size was 2.91. The county population contained 24.00% under the age of 18, 7.70% from 18 to 24, 26.30% from 25 to 44, 22.80% from 45 to 64, and 19.20% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 94.10 males. For every 100 females age 18 and over, there were 91.40 males. The median income for a household in the county was $34,908, and the median income for a family was $43,072. Males had a median income of $29,680 versus $21,305 for females. The per capita income for the county was $17,190. About 6.60% of families and 8.70% of the population were below the poverty line, including 9.70% of those under age 18 and 8.00% of those age 65 or over.
Prior to 1940, Gage County was a swing county, backing the national winner in every presidential election from 1900 to 1936. Since then, it has become a Republican stronghold, aside from the 1964 election in which Democrat Lyndon B. Johnson won the county in the midst of his national landslide victory.
