Menominee County is part of the Marinette, WI–MI Micropolitan Statistical Area.
As of the census of 2000, there were 25,326 people, 10,529 households, and 7,001 families residing in the county. The population density was 24 people per square mile (9/km²). There were 13,639 housing units at an average density of 13 per square mile (5/km²). The racial makeup of the county was 96.24% White, 0.10% Black or African American, 2.27% Native American, 0.21% Asian, 0.18% from other races, and 0.98% from two or more races. 0.75% of the population were Hispanic or Latino of any race. 27.4% were of German, 11.3% French, 9.9% Polish, 8.4% Swedish, 7.1% French Canadian and 5.4% Irish ancestry according to Census 2000. 96.9% spoke English and 1.1% Spanish as their first language.
There were 10,529 households out of which 28.90% had children under the age of 18 living with them, 53.80% were married couples living together, 8.80% had a female householder with no husband present, and 33.50% were non-families. 29.20% of all households were made up of individuals and 13.20% 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.
In the county the population was spread out with 24.00% under the age of 18, 7.60% from 18 to 24, 26.20% from 25 to 44, 24.90% from 45 to 64, and 17.30% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 98.90 males. For every 100 females age 18 and over, there were 97.40 males.
The median income for a household in the county was $32,888, and the median income for a family was $40,268. Males had a median income of $31,975 versus $21,837 for females. The per capita income for the county was $16,909. About 8.00% of families and 11.50% of the population were below the poverty line, including 15.60% of those under age 18 and 11.10% of those age 65 or over.