Iowa was admitted to the Union on December 28, 1846, and elects United States senators to class 2 and class 3. The state's current U.S. senators are Republicans Chuck Grassley (serving since 1981) and Joni Ernst (serving since 2015). Chuck Grassley is Iowa's longest-serving senator (since 1981).
|- style="height:2em" | rowspan=2 colspan=3 | Vacant | rowspan=2 nowrap | Dec 28, 1846 âÂÂ<br/>Dec 7, 1848 | rowspan=2 | Legislature failed to elect. | rowspan=2 | â | | rowspan=2 | â | rowspan=2 | Legislature failed to elect. | rowspan=2 nowrap | Dec 28, 1846 âÂÂ<br/>Dec 7, 1848 | rowspan=2 colspan=3 | Vacant
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|- style="height:2em" ! rowspan=9 | 1 | rowspan=9 align=left | <br/>George W. Jones<br /> | rowspan=9 | Democratic | rowspan=9 nowrap | Dec 7, 1848 âÂÂ<br/>Mar 3, 1859 | rowspan=3 | Elected in 1848. | rowspan=3 | 1 | 1 | Elected in 1848. | rowspan=4 nowrap | Dec 7, 1848 âÂÂ<br/>Feb 22, 1855 | rowspan=4 | Democratic | rowspan=4 align=right | <br/>Augustus C. Dodge<br /> ! rowspan=4 | 1
|- style="height:2em" | | rowspan=4 | 2 | rowspan=3 | Re-elected in 1849.Resigned to become U.S. Minister to Spain, having lost re-election.
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|- style="height:2em" | rowspan=6 | Re-elected in 1852.Lost renomination. | rowspan=6 | 2 | rowspan=2
|- style="height:2em" | | nowrap | Feb 22, 1855 âÂÂ<br/>Mar 3, 1855 | colspan=3 | Vacant
|- style="height:2em" | rowspan=3 | rowspan=5 | 3 | Elected in 1855.Elected invalidated, as the Iowa Senate had not participated in it. | nowrap | Mar 4, 1855 âÂÂ<br/>Jan 5, 1857 | | Free Soil | align=right | <br/>James Harlan<br /> ! rowspan=8 | 2
|- style="height:2em" | | nowrap | Jan 5, 1857 âÂÂ<br/>Jan 29, 1857 | colspan=2 | Vacant
|- style="height:2em" | rowspan=3 | Re-elected to finish his vacant term. | rowspan=6 nowrap | Jan 29, 1857 âÂÂ<br/>May 15, 1865 | rowspan=6 | Republican | rowspan=6 align=right | <br/>James Harlan<br />
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|- style="height:2em" ! rowspan=8 | 2 | rowspan=8 align=left | <br/>James W. Grimes<br /> | rowspan=8 | Republican | rowspan=8 nowrap | Mar 4, 1859 âÂÂ<br/>Dec 6, 1869 | rowspan=3 | Elected in 1858. | rowspan=3 | 3 |
|- style="height:2em" | | rowspan=5 | 4 | rowspan=3 |Re-elected in 1860.Resigned to become U.S. Secretary of the Interior.
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|- style="height:2em" | rowspan=5 | Re-elected in 1864.Resigned due to ill health. | rowspan=7 | 4 | rowspan=3
|- style="height:2em" | | nowrap | May 15, 1865 âÂÂ<br/>Jan 13, 1866 | colspan=3 | Vacant
|- style="height:2em" | Elected to finish Harlan's term.Lost nomination for the next term. | nowrap | Jan 13, 1866 âÂÂ<br/>Mar 3, 1867 | | Republican | align=right | <br/>Samuel J. Kirkwood<br /> ! 3
|- style="height:2em" | | rowspan=5 | 5 | rowspan=5 | Elected in 1866.Lost re-election. | rowspan=5 nowrap | Mar 4, 1867 âÂÂ<br/>Mar 3, 1873 | rowspan=5 | Republican | rowspan=5 align=right | <br/>James Harlan<br /> ! rowspan=5 | 4
|- style="height:2em" | rowspan=3
|- style="height:2em" | colspan=3 | Vacant | nowrap | Dec 6, 1869 âÂÂ<br/>Jan 18, 1870 |
|- style="height:2em" ! 3 | align=left | <br/>James B. Howell<br /> | | Republican | nowrap | Jan 18, 1870 âÂÂ<br/>Mar 3, 1871 | Elected to finish Grimes's term.Retired.
|- style="height:2em" ! rowspan=3 | 4 | rowspan=3 align=left | <br/>George G. Wright<br /> | rowspan=3 | Republican | rowspan=3 nowrap | Mar 4, 1871 âÂÂ<br/>Mar 3, 1877 | rowspan=3 | Elected in 1870.Retired. | rowspan=3 | 5 |
|- style="height:2em" | | rowspan=3 | 6 | rowspan=3 | Elected in 1872. | rowspan=21 nowrap | Mar 4, 1873 âÂÂ<br/>Aug 4, 1908 | rowspan=21 | Republican | rowspan=21 align=right | <br/>William B. Allison<br /> ! rowspan=21 | 5
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|- style="height:2em" ! rowspan=3 | 5 | rowspan=3 align=left | <br/>Samuel J. Kirkwood<br /> | rowspan=3 | Republican | rowspan=3 nowrap | Mar 4, 1877 âÂÂ<br/>Mar 7, 1881 | rowspan=3 | Elected in 1876 or 1877.Resigned to become U.S. Secretary of the Interior. | rowspan=4 | 6 |
|- style="height:2em" | | rowspan=4 | 7 | rowspan=4 | Re-elected in 1878.
|- style="height:2em" | rowspan=2
|- style="height:2em" ! 6 | align=left | <br/>James W. McDill<br /> | | Republican | nowrap | Mar 8, 1881 âÂÂ<br/>Mar 3, 1883 | Appointed to continue Kirkwood's term.Elected in 1882 to finish Kirkwood's term.Retired.
|- style="height:2em" ! rowspan=6 | 7 | rowspan=6 align=left | <br/>James F. Wilson<br /> | rowspan=6 | Republican | rowspan=6 nowrap | Mar 4, 1883 âÂÂ<br/>Mar 3, 1895 | rowspan=3 | Elected in 1882. | rowspan=3 | 7 |
|- style="height:2em" | | rowspan=3 | 8 | rowspan=3 | Re-elected in 1884.
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|- style="height:2em" | rowspan=3 | Re-elected in 1888.Retired. | rowspan=3 | 8 |
|- style="height:2em" | | rowspan=3 | 9 | rowspan=3 | Re-elected in 1890.
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|- style="height:2em" ! rowspan=3 | 8 | rowspan=3 align=left | <br/>John H. Gear<br /> | rowspan=3 | Republican | rowspan=3 nowrap | Mar 4, 1895 âÂÂ<br/>Jul 14, 1900 | rowspan=3 | Elected in 1894.Re-elected in 1900, but died. | rowspan=5 | 9 |
|- style="height:2em" | | rowspan=5 | 10 | rowspan=5 | Re-elected in 1896.
|- style="height:2em" | rowspan=3
|- style="height:2em" | colspan=3 | Vacant | nowrap | Jul 14, 1900 âÂÂ<br/>Aug 22, 1900 |
|- style="height:2em" ! rowspan=8 | 9 | rowspan=8 align=left | <br/>Jonathan P. Dolliver<br /> | rowspan=8 | Republican | rowspan=8 nowrap | Aug 22, 1900 âÂÂ<br/>Oct 15, 1910 | Appointed to finish Gear's term.
|- style="height:2em" | rowspan=3 | Appointed to begin the vacant term.Elected in 1902 to finish the vacant term. | rowspan=3 | 10 |
|- style="height:2em" | | rowspan=5 | 11 | rowspan=3 | Re-elected in 1902.Renominated in 1908 but died before the general election.
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|- style="height:2em" | rowspan=4 | Re-elected in 1907.Died. | rowspan=8 | 11 | rowspan=3
|- style="height:2em" | | nowrap | Aug 4, 1908 âÂÂ<br/>Nov 24, 1908 | colspan=3 | Vacant
|- style="height:2em" | Elected to finish Allison's term. | rowspan=16 nowrap | Nov 24, 1908 âÂÂ<br/>Jul 30, 1926 | rowspan=16 | Republican | rowspan=16 align=right | <br/>Albert B. Cummins<br /> ! rowspan=16 | 6
|- style="height:2em" | rowspan=3 | rowspan=6 | 12 | rowspan=6 | Re-elected in 1909.
|- style="height:2em" | colspan=3 | Vacant | nowrap | Oct 15, 1910 âÂÂ<br/>Nov 12, 1910 |
|- style="height:2em" ! rowspan=2 | 10 | rowspan=2 align=left | <br/>Lafayette Young<br /> | rowspan=2 | Republican | rowspan=2 nowrap | Nov 12, 1910 âÂÂ<br/>Apr 11, 1911 | rowspan=2 | Appointed to continue Dolliver's term.Lost election to finish Dolliver's term.
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|- style="height:2em" ! rowspan=6 | 11 | rowspan=6 align=left | <br/>William S. Kenyon<br /> | rowspan=6 | Republican | rowspan=6 nowrap | Apr 12, 1911 âÂÂ<br/>Feb 24, 1922 | rowspan=1 | Elected to finish Dolliver's term.
|- style="height:2em" | rowspan=3 | Re-elected in 1913. | rowspan=3 | 12 |
|- style="height:2em" | | rowspan=3 | 13 | rowspan=3 | Re-elected in 1914.
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|- style="height:2em" | rowspan=2 | Re-elected in 1918.Resigned to become Judge of the U.S. Court of Appeals. | rowspan=5 | 13 |
|- style="height:2em" | rowspan=3 | rowspan=8 | 14 | rowspan=6 | Re-elected in 1920.Lost renomination, then died.
|- style="height:2em" ! 12 | align=left | <br/>Charles A. Rawson<br /> | | Republican | nowrap | Feb 24, 1922 âÂÂ<br/>Dec 1, 1922 | Appointed to continue Kenyon's term.Retired when his successor was elected.
|- style="height:2em" ! rowspan=3 | 13 | rowspan=3 align=left | <br/>Smith W. Brookhart<br /> | rowspan=3 | Republican | rowspan=3 nowrap | Dec 1, 1922 âÂÂ<br/>Apr 12, 1926 | rowspan=2 | Elected to finish Kenyon's term.
|- style="height:2em" |
|- style="height:2em" | Re-elected in 1924.Lost election challenge. | rowspan=6 | 14 | rowspan=4
|- style="height:2em" ! rowspan=5 | 14 | rowspan=5 align=left | <br/>Daniel F. Steck<br /> | rowspan=5 | Democratic | rowspan=5 nowrap | Apr 12, 1926 âÂÂ<br/>Mar 3, 1931 | rowspan=5 | Successfully challenged his predecessor's election.Lost re-election.
|- style="height:2em" | | nowrap | Jul 30, 1926 âÂÂ<br/>Aug 7, 1926 | colspan=3 | Vacant
|- style="height:2em" | Appointed to continue Cummins's term.Elected in 1926 to finish Cummins's term.Retired. | nowrap | Aug 7, 1926 âÂÂ<br/>Mar 3, 1927 | | Republican | align=right | <br/>David W. Stewart<br /> ! 7
|- style="height:2em" | | rowspan=3 | 15 | rowspan=3 | Elected in 1926.Lost renomination and then lost re-election as an Independent. | rowspan=3 nowrap | Mar 4, 1927 âÂÂ<br/>Mar 3, 1933 | rowspan=3 | Republican | rowspan=3 align=right | <br/>Smith W. Brookhart<br /> ! rowspan=3 | 8
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|- style="height:2em" ! rowspan=5 | 15 | rowspan=5 align=left | <br/>L. J. Dickinson<br /> | rowspan=5 | Republican | rowspan=5 nowrap | Mar 4, 1931 âÂÂ<br/>Jan 3, 1937 | rowspan=5 | Elected in 1930.Lost re-election. | rowspan=5 | 15 |
|- style="height:2em" | | rowspan=5 | 16 | rowspan=2 | Elected in 1932.Died. | rowspan=2 nowrap | Mar 4, 1933 âÂÂ<br/>Jul 16, 1936 | rowspan=2 | Democratic | rowspan=2 align=right | <br/>Louis Murphy<br /> ! rowspan=2 | 9
|- style="height:2em" | rowspan=3
|- style="height:2em" | | nowrap | Jul 16, 1936 âÂÂ<br/>Nov 3, 1936 | colspan=3 | Vacant
|- style="height:2em" | rowspan=2 | Elected to finish Murphy's term. | rowspan=5 nowrap | Nov 3, 1936 âÂÂ<br/>Jan 3, 1945 | rowspan=5 | Democratic | rowspan=5 align=right | <br/>Guy Gillette<br /> ! rowspan=5 | 10
|- style="height:2em" ! rowspan=3 | 16 | rowspan=3 align=left | <br/>Clyde L. Herring<br /> | rowspan=3 | Democratic | rowspan=3 nowrap | Jan 3, 1937 âÂÂ<br/>Jan 3, 1943 | rowspan=3 | Elected in 1936.<br/>Did not take seat until Jan 15, 1937 in order to remain Governor of Iowa.Lost re-election. | rowspan=3 | 16 |
|- style="height:2em" | | rowspan=3 | 17 | rowspan=3 | Re-elected in 1938.Lost re-election.
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|- style="height:2em" ! rowspan=3 | 17 | rowspan=3 align=left | <br/>George A. Wilson<br /> | rowspan=3 | Republican | rowspan=3 nowrap | Jan 3, 1943 âÂÂ<br/>Jan 3, 1949 | rowspan=3 | Elected in 1942.<br/>Did not take seat until Jan 14, 1943 in order to remain Governor of Iowa.Lost re-election. | rowspan=3 | 17 |
|- style="height:2em" | | rowspan=3 | 18 | rowspan=3 | Elected in 1944. | rowspan=12 nowrap | Jan 3, 1945 âÂÂ<br/>Jan 3, 1969 | rowspan=12 | Republican | rowspan=12 align=right | <br/>Bourke B. Hickenlooper<br /> ! rowspan=12 | 11
|- style="height:2em" |
|- style="height:2em" ! rowspan=3 | 18 | rowspan=3 align=left | <br/>Guy Gillette<br /> | rowspan=3 | Democratic | rowspan=3 nowrap | Jan 3, 1949 âÂÂ<br/>Jan 3, 1955 | rowspan=3 | Elected in 1948.Lost re-election. | rowspan=3 | 18 |
|- style="height:2em" | | rowspan=3 | 19 | rowspan=3 | Re-elected in 1950.
|- style="height:2em" |
|- style="height:2em" ! rowspan=3 | 19 | rowspan=3 align=left | <br/>Thomas E. Martin<br /> | rowspan=3 | Republican | rowspan=3 nowrap | Jan 3, 1955 âÂÂ<br/>Jan 3, 1961 | rowspan=3 | Elected in 1954.Retired. | rowspan=3 | 19 |
|- style="height:2em" | | rowspan=3 | 20 | rowspan=3 | Re-elected in 1956.
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|- style="height:2em" ! rowspan=6 | 20 | rowspan=6 align=left | <br/>Jack Miller<br /> | rowspan=6 | Republican | rowspan=6 nowrap | Jan 3, 1961 âÂÂ<br/>Jan 3, 1973 | rowspan=3 | Elected in 1960. | rowspan=3 | 20 |
|- style="height:2em" | | rowspan=3 | 21 | rowspan=3 | Re-elected in 1962Retired.
|- style="height:2em" |
|- style="height:2em" | rowspan=3 | Re-elected in 1966.Lost re-election. | rowspan=3 | 21 |
|- style="height:2em" | | rowspan=3 | 22 | rowspan=3 | Elected in 1968.Retired. | rowspan=3 nowrap | Jan 3, 1969 âÂÂ<br/>Jan 3, 1975 | rowspan=3 | Democratic | rowspan=3 align=right | <br/>Harold Hughes<br /> ! rowspan=3 | 12
|- style="height:2em" |
|- style="height:2em" ! rowspan=3 | 21 | rowspan=3 align=left | <br/>Dick Clark<br /> | rowspan=3 | Democratic | rowspan=3 nowrap | Jan 3, 1973 âÂÂ<br/>Jan 3, 1979 | rowspan=3 | Elected in 1972.Lost re-election. | rowspan=3 | 22 |
|- style="height:2em" | | rowspan=3 | 23 | rowspan=3 | Elected in 1974.Lost re-election. | rowspan=3 nowrap | Jan 3, 1975 âÂÂ<br/>Jan 3, 1981 | rowspan=3 | Democratic | rowspan=3 align=right | <br/>John Culver<br /> ! rowspan=3 | 13
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|- style="height:2em" ! rowspan=3 | 22 | rowspan=3 align=left | <br/>Roger Jepsen<br /> | rowspan=3 | Republican | rowspan=3 nowrap | Jan 3, 1979 âÂÂ<br/>Jan 3, 1985 | rowspan=3 | Elected in 1978.Lost re-election. | rowspan=3 | 23 |
|- style="height:2em" | | rowspan=3 | 24 | rowspan=3 | Elected in 1980. | rowspan=24 nowrap | Jan 3, 1981 âÂÂ<br/>present | rowspan=24 | Republican | rowspan=24 align=right | <br/>Chuck Grassley<br /> ! rowspan=24 | 14
|- style="height:2em" |
|- style="height:2em" ! rowspan=15 | 23 | rowspan=15 align=left | <br/>Tom Harkin<br /> | rowspan=15 | Democratic | rowspan=15 nowrap | Jan 3, 1985 âÂÂ<br/>Jan 3, 2015 | rowspan=3 | Elected in 1984. | rowspan=3 | 24 |
|- style="height:2em" | | rowspan=3 | 25 | rowspan=3 | Re-elected in 1986.
|- style="height:2em" |
|- style="height:2em" | rowspan=3 | Re-elected in 1990. | rowspan=3 | 25 |
|- style="height:2em" | | rowspan=3 | 26 | rowspan=3 | Re-elected in 1992.
|- style="height:2em" |
|- style="height:2em" | rowspan=3 | Re-elected in 1996. | rowspan=3 | 26 |
|- style="height:2em" | | rowspan=3 | 27 | rowspan=3 | Re-elected in 1998.
|- style="height:2em" |
|- style="height:2em" | rowspan=3 | Re-elected in 2002. | rowspan=3 | 27 |
|- style="height:2em" | | rowspan=3 | 28 | rowspan=3 | Re-elected in 2004.
|- style="height:2em" |
|- style="height:2em" | rowspan=3 | Re-elected in 2008Retired. | rowspan=3 | 28 |
|- style="height:2em" | | rowspan=3 | 29 | rowspan=3 | Re-elected in 2010.
|- style="height:2em" |
|- style="height:2em" ! rowspan=6 | 24 | rowspan=6 align=left | <br/>Joni Ernst<br /> | rowspan=6 | Republican | rowspan=6 nowrap | Jan 3, 2015 âÂÂ<br/>present | rowspan=3 | Elected in 2014. | rowspan=3 | 29 |
|- style="height:2em" | | rowspan=3 | 30 | rowspan=3 | Re-elected in 2016.
|- style="height:2em" |
|- style="height:2em" | rowspan=3 |Re-elected in 2020.Retiring at the end of term. | rowspan=3 | 30 |
|- style="height:2em" | | rowspan=3|31 | rowspan=3| Re-elected in 2022.
|- style="height:2em" |
|- style="height:2em" | rowspan=2 colspan=5 | To be determined in the 2026 election. | rowspan=2 | 31 |
|- style="height:2em" | | 32 | colspan=5 | To be determined in the 2028 election.