Madison County is part of the Norfolk, Nebraska, Micropolitan Statistical Area.
In the Nebraska license plate system, Madison County is represented by the prefix 7 (it had the seventh-largest number of vehicles registered in the county when the license plate system was established in 1922).
1870 - 1,133 1880 - 5,589 1890 - 13,669 1900 - 16,976 1910 - 19,101 1920 - 22,511 1930 - 26,037 1940 - 24,269 1950 - 24,338 1960 - 25,145 1970 - 27,402 1980 - 31,382 1990 - 32,655 2000 - 35,226
As of the census of 2000, there were 35,226 people, 13,436 households, and 8,894 families residing in the county. The population density was 62 people per square mile (24/km²). There were 14,432 housing units at an average density of 25 per square mile (10/km²). The racial makeup of the county was 91.35% White, 0.94% Black or African American, 1.19% Native American, 0.40% Asian, 0.03% Pacific Islander, 5.06% from other races, and 1.03% from two or more races. 8.64% of the population were Hispanic or Latino of any race.
There were 13,436 households out of which 33.20% had children under the age of 18 living with them, 54.70% were married couples living together, 8.40% had a female householder with no husband present, and 33.80% were non-families. 27.90% of all households were made up of individuals and 12.40% had someone living alone who was 65 years of age or older. The average household size was 2.52 and the average family size was 3.12.
In the county the population was spread out with 26.80% under the age of 18, 11.60% from 18 to 24, 27.10% from 25 to 44, 20.10% from 45 to 64, and 14.40% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 98.50 males. For every 100 females age 18 and over, there were 94.80 males.
The median income for a household in the county was $35,807, and the median income for a family was $45,073. Males had a median income of $30,631 versus $21,343 for females. The per capita income for the county was $16,804. About 7.50% of families and 11.20% of the population were below the poverty line, including 13.00% of those under age 18 and 11.50% of those age 65 or over.