Iowa's 18th Senate district
The 18th District of the Iowa Senate is located in central Iowa, and is currently composed of part of Polk County.
Current elected officials
Janet Petersen is the senator currently representing the 18th District.The area of the 18th District contains two Iowa House of Representatives districts:
- The 35th District
- The 36th District
Historical district boundaries
Source:| Map | Description | Years effective | Notes |
| Cedar County Clinton County | 1852-1855 | From 1846 to 1857, district numbering was not utilized by the Iowa State Legislature. This convention was added with the passing of the 1857 Iowa Constitution. Numbering of districts pre-1857 is done as a matter of historic convenience. | |
| Adair County Cass County Madison County Warren County | 1856-1859 | ||
| Marion County | 1860-1863 | ||
| Mahaska County | 1864-1877 | ||
| Adair County Cass County Madison County | 1878-1883 | ||
| Adair County Adams County Cass County | 1884-1887 | ||
| Cass County Shelby County | 1888-1962 | ||
| Clinton County | 1963-1966 | ||
| Iowa County Poweshiek County | 1967-1970 | ||
| Grundy County Marshall County | 1971-1972 | In 1970, the Iowa Legislature passed an amendment to the Iowa Constitution setting forth the rules for legislative redistricting in order to abide by the rules established by the Reynolds v. Sims Supreme Court case. The first reapportionment map created by the Republican controlled legislature was deemed unconstitutional, but was still used for the 1970 election. | |
Black Hawk County
| 1973-1982 | ||
| Dubuque County | 1983-2002 | Some minor boundary changes may have occurred after the redistricting of 1992. | |
| Linn County | 2003-2012 | ||
| Polk County | 2013-2022 | ||
| Polk County | 2023-present | - |