Ida County is situated in the northwestern part of Iowa, lying in the second tier of counties east of the Missouri River and in the fourth tier south of the Iowa-Minnesota line. Ida Grove, the county seat and largest town, is 50 miles east and a little south of Sioux City, 80 miles northeast of Council Bluffs and 110 miles northwest of Des Moines. The county lies in the eastern part of a rolling, loess-covered plain which, in places, reaches a width of 100 miles along the western boundary of Iowa. All of Ida County lies within the drainage basin of the Missouri River, and the major part of the county is drained by the Maple River and its tributaries.