Iowa has 99 counties and 5 congressional districts: all 99 counties are "undivided- that is, they are all wholly within a given congressional district.
- CD # 1: Cedar, Clinton, Johnson, Jones, Linn, Louisa, Muscatine and Scott
- CD # 2: Allamakee, Benton, Black Hawk, Bremer, Buchanan, Butler, Cerro Gordo, Chickasaw, Clayton, Delaware, Dubuque, Fayette, Floyd, Grundy, Howard, Iowa, Jackson, Mitchell, Tama, Winneshiek and Worth
- CD # 3: Adams, Appanoose, Clarke, Davis, Decatur, Des Moines, Henry, Jasper, Jefferson, Keokuk, Lee, Lucas, Mahoska, Marion, Marshall, Monroe, Page, Poweshiek, Ringgold, Story, Taylor, Union, Van Buren, Wapello, Warren, Washington and Wayne
- CD # 4: Adair, Audubon, Cass, Dallas, Fremont, Guthrie, Harrison, Madison, Mills, Montgomery, Polk, Pottawatamie and Shelby
- CD # 5: Boone, Buena Vista, Calhoun, Carroll, Cherokee, Clay, Crawford, Dickinson, Emmet, Franklin, Greene, Hamilton, Hancock, Hardin, Humboldt, Ida, Kossuth, Lyon, Monona, O'Brien, Osceola, Palo Alto, Plymouth, Pocahontas, Sac, Sioux, Webster, Winnebago, Woodbury and Wright