Ingham County was established by an act of the Michigan Territorial Legislature on October 29, 1829, from portions of Shiawassee County, Washtenaw County and unorganized territory. It was attached for administrative purposes to Washtenaw County until 1838 when county government was established for Ingham.
The county is named for Samuel D. Ingham, the U.S. Secretary of the Treasury under President Andrew Jackson, making Ingham one of the so-called Cabinet counties.
As of the census of 2000, there were 279,320 people, 108,593 households, and 63,744 families residing in the county. The population density was 500 people per square mile (193/km²). There were 115,056 housing units at an average density of 206 per square mile (79/km²). The racial makeup of the county was 79.46% White, 10.86% Black or African American, 0.55% Native American, 3.68% Asian, 0.05% Pacific Islander, 2.42% from other races, and 2.99% from two or more races. 5.80% of the population were Hispanic or Latino of any race. 18.7% were of German, 10.1% English, 8.4% Irish and 6.4% American ancestry according to Census 2000. 90.0% spoke English and 3.8% Spanish as their first language.
There were 108,593 households out of which 29.80% had children under the age of 18 living with them, 43.00% were married couples living together, 12.10% had a female householder with no husband present, and 41.30% were non-families. 30.20% of all households were made up of individuals and 7.70% had someone living alone who was 65 years of age or older. The average household size was 2.42 and the average family size was 3.04.
In the county the population was spread out with 23.40% under the age of 18, 18.50% from 18 to 24, 28.60% from 25 to 44, 20.10% from 45 to 64, and 9.40% who were 65 years of age or older. The median age was 30 years. For every 100 females there were 93.30 males. For every 100 females age 18 and over, there were 90.10 males.
The median income for a household in the county was $40,774, and the median income for a family was $53,063. Males had a median income of $40,335 versus $30,178 for females. The per capita income for the county was $21,079. About 8.30% of families and 14.60% of the population were below the poverty line, including 14.60% of those under age 18 and 6.60% of those age 65 or over.