Barry County was formed by an act of the legislature of the Michigan Territory on April 29, 1829. The name comes from William Taylor Barry, United States Postmaster General under President Andrew Jackson, making it one of Michigan's "cabinet counties".
As of the 2000 census, there were 56,755 people, 21,035 households, and 15,986 families residing in the county. The population density was 102 people per square mile (39/km²). There were 23,876 housing units at an average density of 43 per square mile (17/km²). The racial makeup of the county was 97.39% White, 0.24% African American, 0.46% Native American, 0.27% Asian, 0.01% Pacific Islander, 0.50% from other races, and 1.12% from two or more races. 1.46% of the population were Hispanic or Latino of any race. 21.8% were of German, 13.6% English, 12.5% Dutch, 12.4% American and 9.6% Irish ancestry according to Census 2000. 98.2% spoke English as their first language.
There were 21,035 households out of which 35.20% had children under the age of 18 living with them, 64.10% were married couples living together, 7.70% had a female householder with no husband present, and 24.00% were non-families. 19.50% 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 2.68 and the average family size was 3.06.
In the county the population was spread out with 27.20% under the age of 18, 7.50% from 18 to 24, 29.00% from 25 to 44, 24.60% from 45 to 64, and 11.80% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 99.70 males. For every 100 females age 18 and over, there were 98.80 males.
The median income for a household in the county was $46,820, and the median income for a family was $51,794. Males had a median income of $38,991 versus $26,387 for females. The per capita income for the county was $20,636. About 3.90% of families and 5.50% of the population were below the poverty line, including 5.90% of those under age 18 and 5.90% of those age 65 or over.