The Iowa Legislature authorized the formation of 49 counties in previously–unregulated western Iowa on 15 January 1851. This date is usually cited as the date of formation of Ida County; however, as there were no inhabitants of that area, no action was taken to form a county government.
On 12 January 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. In 1853 there were still no settlers in Ida County's lands.
The county's first permanent settlers (Comstock and Moorehead) arrived in 1856. In 1858 the county government was organized, with John Moorehead appointed County Judge. There were about 40 county residents at that time.
The county's only postoffice, as well as the first courthouse, was operated from Judge Moorehead's house.
The county's first dedicated school building was raised in 1861.
The county's first newspaper, Ida County Pioneer, was started in 1872. The first bank opened in 1876. Railroads arrived in Ida County in 1877, when the Maple Valley branch of the Chicago & North Western Railway was built. This resulted in a flood of settlers, and within five years, nearly all the available land had been purchased