As of the census² of 2000, there were 1,116,200 people, 456,129 households, and 267,291 families residing in the county. The population density was 774/km² (2,005/mi²). There were 468,824 housing units at an average density of 325/km² (842/mi²). The racial makeup of the county was 80.53% White, 8.95% Black or African American, 1.00% Native American, 4.80% Asian, 0.05% Pacific Islander, 2.06% from other races, and 2.60% from two or more races. 4.07% of the population were Hispanic or Latino of any race. 22.8% were of German, 12.0% Norwegian, 7.6% Irish and 7.2% Swedish ancestry according to Census 2000. There were 456,129 households out of which 28.80% had children under the age of 18 living with them, 45.30% were married couples living together, 9.90% had a female householder with no husband present, and 41.40% were non-families. 31.80% of all households were made up of individuals and 8.40% had someone living alone who was 65 years of age or older. The average household size was 2.39 and the average family size was 3.07.
In the county the population was spread out with 24.00% under the age of 18, 9.70% from 18 to 24, 33.70% from 25 to 44, 21.70% from 45 to 64, and 11.00% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 97.00 males. For every 100 females age 18 and over, there were 94.70 males.
The median income for a household in the county was $51,711, and the median income for a family was $65,985 (these figures had risen to $60,115 and $79,970 respectively as of a 2007 estimate). Males had a median income of $42,466 versus $32,400 for females. The per capita income for the county was $28,789. About 5.00% of families and 8.30% of the population were below the poverty line, including 10.50% of those under age 18 and 5.90% of those age 65 or over.
Hennepin County is the wealthiest county in the state of Minnesota and one of the 100 Highest-income counties in the United States.