| CONGRESS | SENATOR | TERM BEGAN | TERM ENDED | COMMENTS |
|---|---|---|---|---|
| Class 2 | ||||
| 15th-20th | Jesse B. Thomas (R, CRR, ADAMS) | Dec. 3, 1818 | Mar. 3, 1829 | |
| 21st | John McLean (J) | Mar. 4, 1829 | Oct. 14, 1830 | Died |
| 21st | David J. Baker (D) | Nov. 12, 1830 | Dec. 11, 1830 | Appointed |
| 21st-26th | John M. Robinson (J, D) | Dec. 11, 1830 | Mar. 3, 1841 | |
| 27th-28th | Samuel McRoberts (D) | Mar. 4, 1841 | Mar. 27, 1843 | Died |
| 28th-29th | James Semple (D) | Aug. 16, 1843 | Mar. 3, 1847 | Appointed, then elected |
| 30th-37th | Stephen A. Douglas (D) | Mar. 4, 1847 | Jun. 3, 1861 | Died |
| 37th | Orville H. Browning (R) | Jun. 26, 1861 | Jan. 12, 1863 | Appointed |
| 37th-38th | William A. Richardson (D) | Jan. 30, 1863 | Mar. 3, 1865 | |
| 39th-41st | Richard Yates (R) | Mar. 4, 1865 | Mar. 3, 1871 | |
| 42nd-44th | John A. Logan (R) | Mar. 4, 1871 | Mar. 3, 1877 | |
| 45th-47th | David Davis (I) | Mar. 4, 1877 | Mar. 3, 1883 | |
| 48th-62nd | Shelby M. Cullom (R) | Mar. 4, 1883 | Mar. 3, 1913 | |
| 63rd-65th | James Hamilton Lewis (D) | Mar. 26, 19131 | Mar. 3, 1919 | |
| 66th-68th | Joseph Medill McCormick (R) | Mar. 4, 1919 | Feb. 25, 1925 | Died |
| 68th-71st | Charles S. Deneen (R) | Feb. 26, 19252 | Mar. 3, 1931 | |
| 72nd-76th | James Hamilton Lewis (D) | Mar. 4, 1931 | Apr. 9, 1939 | Died |
| 76th | James M. Slattery (D) | Apr. 14, 1939 | Nov. 21, 1940 | Appointed |
| 76th-80th | C. Wayland Brooks (R) | Nov. 22, 1940 | Jan. 3, 1949 | |
| 81st-89th | Paul H. Douglas (D) | Jan. 3, 1949 | Jan. 3, 1967 | |
| 90th-98th | Charles H. Percy (R) | Jan. 3, 1967 | Jan. 3, 1985 | |
| 99th-104th | Paul M. Simon (D) | Jan. 3, 1985 | Jan. 3, 1997 | |
| 105th- | Richard J. Durbin (D) | Jan. 3, 1997 | Present | |
| Class 3 | ||||
| 15th-18th | Ninian Edwards (R, ADAMS-CLAY R) | Dec. 3, 1818 | Mar. 4, 1824 | Resigned |
| 18th | John McLean (CRR) | Nov. 23, 1824 | Mar. 3, 1825 | |
| 19th-24th | Elias K. Kane (J) | Mar. 4, 1825 | Dec. 11, 1835 | Died |
| 24th | William Lee D. Ewing (J) | Dec. 30, 1835 | Mar. 3, 1837 | |
| 25th-27th | Richard M. Young (D) | Mar. 4, 1837 | Mar. 3, 1843 | |
| 28th-30th | Sidney Breese (D) | Mar. 4, 1843 | Mar. 3, 1849 | |
| 31st-33rd | James Shields (D) | Oct. 27, 18493 | Mar. 3, 1855 | |
| 34th-42nd | Lyman Trumbull (D, R) | Mar. 4, 1855 | Mar. 3, 1873 | |
| 43rd-45th | Richard J. Oglesby (R) | Mar. 4, 1873 | Mar. 3, 1879 | |
| 46th-49th | John A. Logan (R) | Mar. 4, 1879 | Dec. 26, 1886 | Died |
| 49th-51st | Charles B. Farwell (R) | Jan. 19, 1887 | Mar. 3, 1891 | |
| 52nd-54th | John McAuley Palmer (D) | Mar. 4, 1891 | Mar. 3, 1897 | |
| 55th-57th | William E. Mason (R) | Mar. 4, 1897 | Mar. 3, 1903 | |
| 58th-60th | Albert J. Hopkins (R) | Mar. 4, 1903 | Mar. 3, 1909 | |
| 61st-63rd | William Lorimer (R) | Jun. 18, 19094 | Jul. 13, 1912 | |
| 63rd-66th | Lawrence Y. Sherman (R) | Mar. 26, 19135 | Mar. 3, 1921 | |
| 67th-69th | William B. McKinley (R) | Mar. 4, 1921 | Dec. 7, 1926 | Died |
| 70th-72nd | Frank L. Smith6 (R) | Mar. 4, 1927 | Feb. 9, 1928 | |
| 71st-72nd | Otis F. Glenn (R) | Dec. 3, 1928 | Mar. 3, 1933 | |
| 73rd-75th | William H. Dieterich (D) | Mar. 4, 1933 | Jan. 3, 1939 | |
| 76th-81st | Scott W. Lucas (D) | Jan. 3, 1939 | Jan. 2, 1951 | |
| 82nd-91st | Everett McKinley Dirksen (R) | Jan. 3, 1951 | Sept. 7, 1969 | Died |
| 91st | Ralph Tyler Smith (R) | Sept. 17, 1969 | Nov. 16, 1970 | Appointed |
| 91st-96th | Adlai E. Stevenson III (D) | Nov. 17, 1970 | Jan. 3, 1981 | |
| 97th-102nd | Alan J. Dixon (D) | Jan. 3, 1981 | Jan. 3, 1993 | |
| 103rd-105th | Carol Moseley-Braun (D) | Jan. 3, 1993 | Jan. 3, 1999 | |
| 106th-108th | Peter G. Fitzgerald (R) | Jan. 3, 1999 | Jan. 3, 2005 | |
| 109th-110th | Barack Obama (D) | Jan. 3, 2005 | Nov. 16, 2008 | Resigned |
| 111th | Roland Burris (D) | Jan. 12, 20097 | Nov. 29, 2010 | Appointed |
| 111th-114th | Mark S. Kirk (R) | Nov. 29, 20108 | Jan. 3, 2017 | |
| 115th- | Tammy Duckworth (D) | Jan. 3, 2017 | Present | |
1. Vacancy from Mar. 4 to Mar. 25, 1913, because of recess of legislature.
2. Elected Nov. 4, 1924, for full term beginning Mar. 4, 1925; subsequently appointed by governor to fill vacancy in term ending Mar. 3, 1925.
3. Elected to term commencing Mar. 4, 1849; took his seat on Mar. 6, 1849, but on Mar. 15, 1849, the Senate declared his election void on the ground that he had not been a citizen of the United States the number of years required by the Constitution; immediately elected for the same term. Vacancy from Mar. 16 to Oct. 27, 1849.
4. Vacancy from Mar. 4 to May 27, 1909, because of failure of legislature to elect, and also from May 27 to June 17, 1909, because Mr. Lorimer did not resign his seat in the House of Representatives until the last named date. Election declared invalid July 13, 1912.
5. Vacancy from July 14, 1912, to Mar. 25, 1913, because of recess of legislature.
6. Smith was elected for term beginning Mar. 4, 1927 and was subsequently appointed by the governor on Dec. 16, 1926, to fill vacancy in the term ending Mar. 3, 1927. The oath was not administered due to questions over campaign financing. He was not permitted to qualify for full term beginning Mar. 4, 1927. Resignation sent to governor of Illinois, Feb. 9, 1928. Vacancy from Dec. 8, 1926, to Dec. 2, 1928.
7. Appointed December 31, 2008, to the United States Senate for the term ending January 3, 2011, to fill the vacancy caused by the resignation of Barack Obama, but credentials were not found to be in order until January 12, 2009.
8. Elected in a special election to fill remainder of the term ending Jan. 3, 2011, and simultaneously elected to the full term beginning Jan. 3, 2011.
