It was named after Ida Smith, the first child of European immigrants to be born in this region.

On January 12, 1853, the Legislature authorized creation of Woodbury County, and included the proviso that the area of Ida County be included with Woodbury for revenue, election, and judicial purposes.

[3] The county's first permanent settlers (Comstock and Moorehead) arrived in 1856.

[3] The county's only postoffice, as well as the first courthouse, was operated from Judge Moorehead's house.

Railroads arrived in Ida County in 1877, when the Maple Valley branch of the Chicago & North Western Railway was built.

[14] As of the census[15] of 2000, there were 7,837 people, 3,213 households, and 2,184 families residing in the county.

29.30% of all households were made up of individuals, and 15.90% had someone living alone who was 65 years of age or older.

The population ranking of the following table is based on the 2020 census of Ida County.