Jefferson County lies on the south line of Nebraska. Its south boundary line abuts the north boundary line of the state of Kansas. The terrain of Jefferson County consists of low rolling hills, whose leveled tops are largely used for agriculture. The Little Blue River flows southeastward through the southwestern-middle of the county. The county has a total area of, of which is land and is water.
As of the 2000 United States Census, there were 8,333 people, 3,527 households, and 2,352 families in the county. The population density was 14 people per square mile. There were 3,942 housing units at an average density of 7 per square mile. The racial makeup of the county was 98.42% White, 0.07% Black or African American, 0.38% Native American, 0.17% Asian, 0.04% Pacific Islander, 0.50% from other races, and 0.42% from two or more races. 1.31% of the population were Hispanic or Latino of any race. There were 3,527 households out of which 28.00% had children under the age of 18 living with them, 57.90% were married couplesliving together, 5.80% had a female householder with no husband present, and 33.30% were non-families. 29.60% of all households were made up of individuals and 17.20% had someone living alone who was 65 years of age or older. The average household size was 2.32 and the average family size was 2.85. The county population contained 23.30% under the age of 18, 6.10% from 18 to 24, 23.70% from 25 to 44, 24.30% from 45 to 64, and 22.70% who were 65 years of age or older. The median age was 43 years. For every 100 females there were 95.60 males. For every 100 females age 18 and over, there were 91.80 males. The median income for a household in the county was $32,629, and the median income for a family was $40,747. Males had a median income of $26,929 versus $18,594 for females. The per capita income for the county was $18,380. About 8.00% of families and 8.90% of the population were below the poverty line, including 10.20% of those under age 18 and 8.70% of those age 65 or over.
Jefferson County is strongly Republican, having only backed the Democratic Party presidential candidate four times since 1900, all in years which the party won nationally by a landslide.
