Pennsylvania ratified the United States Constitution on December 12, 1787, and elects its U.S. senators to class 1 and class 3. Officeholders are popularly elected, for a six-year term, beginning January 3. Elections are held the first Tuesday after November 1. Before 1914, they were chosen by the Pennsylvania General Assembly; before 1935, their terms began March 4. The state's current U.S. senators are Democrat John Fetterman (since 2023) and Republican Dave McCormick (since 2025), making it one of four states to have a split Senate delegation, along with Maine, Vermont, and Wisconsin. Arlen Specter was Pennsylvania's longest-serving senator (1981–2011). Pennsylvania is one of eighteen states alongside California, Colorado, Delaware, Georgia, Hawaii, Idaho, Louisiana, Maine, Massachusetts, Minnesota, Missouri, Nevada, Oklahoma, South Carolina, South Dakota, Utah, and West Virginia, to have a younger senior senator and an older junior senator.
List of senators
|- style="height:2em" ! 1 | align=left | William Maclay | | Anti-Admin. | nowrap | Mar 4, 1789 –Mar 3, 1791 | Elected in 1788.Lost re-election. | 1 | | rowspan=6 | 1 | rowspan=6 | Elected in 1788.Retired. | rowspan=6 nowrap | Mar 4, 1789 –Mar 3, 1795 | rowspan=6 | Pro-Admin. | rowspan=6 align=right | Robert Morris ! rowspan=6 | 1
|- style="height:2em" | colspan=3 | Vacant | nowrap | Mar 4, 1791 –Dec 1, 1793 | Legislature failed to elect. | rowspan=6 | 2 | rowspan=2
|- style="height:2em" ! rowspan=2 | 2 | rowspan=2 align=left | Albert Gallatin | rowspan=2 | Anti-Admin. | rowspan=2 nowrap | Dec 2, 1793 –Feb 28, 1794 | rowspan=2 | Elected to finish the vacant term.Election voided.
|- style="height:2em" | rowspan=3
|- style="height:2em" | colspan=3 | Vacant | nowrap | Mar 1, 1794 –Apr 23, 1794
|- style="height:2em" ! rowspan=7 | 3 | rowspan=7 align=left | James Ross | | Pro-Admin. | rowspan=7 nowrap | Apr 24, 1794 –Mar 3, 1803 | rowspan=2 | Elected to finish the vacant term that happened from 1791 to 1793.
|- style="height:2em" | rowspan=6 | Federalist | | rowspan=3 | 2 | rowspan=3 | Elected in 1795.Retired. | rowspan=3 nowrap | Mar 4, 1795 –Mar 3, 1801 | rowspan=3 | Federalist | rowspan=3 align=right | William Bingham ! rowspan=3 | 2
|- style="height:2em" | rowspan=5 | Re-elected in 1797.Retired. | rowspan=5 | 3
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|- style="height:2em" | rowspan=3 | rowspan=5 | 3 | Elected in 1801.Resigned to become Supervisor of Revenue of Pennsylvania. | nowrap | Mar 4, 1801 –Jun 30, 1801 | | Democratic-Republican | align=right | Peter Muhlenberg ! 3
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| nowrap | Jun 30, 1801 –Dec 17, 1801 | colspan=3 | Vacant
|- style="height:2em" | rowspan=3 | Elected to finish Muhlenberg's term.Retired. | rowspan=3 nowrap | Dec 17, 1801 –Mar 3, 1807 | rowspan=3 | Democratic-Republican | rowspan=3 align=right | George Logan ! rowspan=3 | 4
|- style="height:2em" ! rowspan=3 | 4 | rowspan=3 align=left | Samuel Maclay | rowspan=3 | Democratic-Republican | rowspan=3 nowrap | Mar 4, 1803 –Jan 4, 1809 | rowspan=3 | Elected in 1802.Resigned. | rowspan=5 | 4
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|- style="height:2em" | rowspan=3 | rowspan=5 | 4 | rowspan=5 | Elected in 1806.Retired. | rowspan=5 nowrap | Mar 4, 1807 –Mar 3, 1813 | rowspan=5 | Democratic-Republican | rowspan=5 align=right | Andrew Gregg ! rowspan=5 | 5
|- style="height:2em" | colspan=3 | Vacant | nowrap | Jan 4, 1809 –Jan 9, 1809 | Vacant
|- style="height:2em" ! rowspan=4 | 5 | rowspan=4 align=left | Michael Leib | rowspan=4 | Democratic-Republican | rowspan=4 nowrap | Jan 9, 1809 –Feb 14, 1814 | Elected in 1809 to finish Maclay's term, having been elected to the next term., citing Journal of the Pennsylvania House of Representatives, 1808, pp. 174–176.
|- style="height:2em" | rowspan=3 | Elected in 1808.Resigned to become Postmaster of Philadelphia. | rowspan=5 | 5
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|- style="height:2em" | rowspan=3 | rowspan=5 | 5 | rowspan=5 | Elected in 1812., citing Journal of the Pennsylvania State Senate, 1812, pp. 41–43.Retired. | rowspan=5 nowrap | Mar 4, 1813 –Mar 3, 1819 | rowspan=5 | Democratic-Republican | rowspan=5 align=right | Abner Lacock ! rowspan=5 | 6
|- style="height:2em" | colspan=3 | Vacant | nowrap | Feb 14, 1814 –Feb 24, 1814 | |- style="height:2em" ! rowspan=4 | 6 | rowspan=4 align=left | Jonathan Roberts | rowspan=4 | Democratic-Republican | rowspan=4 nowrap | Feb 24, 1814 –Mar 3, 1821 | Elected to finish Leib's term.
|- style="height:2em" | rowspan=3 | Re-elected in late 1814. | rowspan=3 | 6
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|- style="height:2em" | | rowspan=4 | 6 | rowspan=4 | Elected in 1818.Retired. | rowspan=4 nowrap | Mar 4, 1819 –Mar 3, 1825 | rowspan=4 | Democratic-Republican | rowspan=4 align=right | Walter Lowrie ! rowspan=4 | 7
|- style="height:2em" | colspan=3 | Vacant | nowrap | Mar 4, 1821 –Dec 10, 1821 | Legislature failed to elect. | rowspan=4 | 7 | rowspan=2
|- style="height:2em" ! rowspan=3 | 7 | rowspan=3 align=left | William Findlay | rowspan=2 | Democratic-Republican | rowspan=3 nowrap | Dec 10, 1821 –Mar 3, 1827 | rowspan=3 | Elected late in 1821.Retired.
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|- style="height:2em" | | Jacksonian | | rowspan=3 | 7 | rowspan=3 | Elected in 1825.Lost re-election. | rowspan=3 nowrap | Mar 4, 1825 –Mar 3, 1831 | rowspan=3 | NationalRepublican | rowspan=3 align=right | William Marks ! rowspan=3 | 8
|- style="height:2em" ! rowspan=3 | 8 | rowspan=3 align=left | Isaac D. Barnard | rowspan=3 | Jacksonian | rowspan=3 nowrap | Mar 4, 1827 –Dec 6, 1831 | rowspan=3 | Elected in 1826.Resigned to due ill health. | rowspan=5 | 8
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|- style="height:2em" | rowspan=3 | rowspan=8 | 8 | rowspan=5 | Elected in 1830.Resigned to become U.S. Minister to Russia. | rowspan=5 nowrap | Mar 4, 1831 –Jun 30, 1834 | rowspan=5 | Jacksonian | rowspan=5 align=right | William Wilkins ! rowspan=5 | 9
|- style="height:2em" | colspan=3 | Vacant | nowrap | Dec 6, 1831 –Dec 13, 1831
|- style="height:2em" ! 9 | align=left | George M. Dallas | | Jacksonian | nowrap | Dec 13, 1831 –Mar 3, 1833 | Elected to finish Barnard's term.Retired.
|- style="height:2em" | colspan=3 | Vacant | nowrap | Mar 4, 1833 – Dec 7, 1833 | Legislature failed to elect. | rowspan=6 | 9 | rowspan=4
|- style="height:2em" ! rowspan=5 | 10 | rowspan=5 align=left | Samuel McKean | rowspan=4 | Jacksonian | rowspan=5 nowrap | Dec 7, 1833 –Mar 3, 1839 | rowspan=5 | Elected late in 1833.
|- style="height:2em"
| nowrap | Jun 30, 1834 –Dec 6, 1834 | colspan=3 | Vacant
|- style="height:2em" | rowspan=2 | Elected to finish Wilkins's term. | rowspan=8 nowrap | Dec 6, 1834 –Mar 5, 1845 | rowspan=2 | Jacksonian | rowspan=8 align=right | James Buchanan ! rowspan=8 | 10
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|- style="height:2em" | | Democratic | | rowspan=4 | 9 | rowspan=4 | Re-elected in 1836. | rowspan=6 | Democratic
|- style="height:2em" | colspan=3 | Vacant | nowrap | Mar 4, 1839 –Jan 14, 1840 | Legislature failed to elect. | rowspan=4 | 10 | rowspan=2
|- style="height:2em" ! rowspan=8 | 11 | rowspan=8 align=left | Daniel Sturgeon | rowspan=8 | Democratic | rowspan=8 nowrap | Jan 14, 1840 –Mar 3, 1851 | rowspan=3 | Elected late in 1840.
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|- style="height:2em" | | rowspan=5 | 10 | rowspan=2 | Re-elected in 1843.Resigned to become U.S. Secretary of State.
|- style="height:2em" | rowspan=5 | Re-elected in 1845.Retired. | rowspan=5 | 11 | rowspan=3
|- style="height:2em"
| nowrap | Mar 5, 1845 –Mar 13, 1845 | colspan=3 | Vacant
|- style="height:2em" | rowspan=2 | Elected in 1845 to finish Buchanan's term.Retired. | rowspan=2 nowrap | Mar 13, 1845 –Mar 3, 1849 | rowspan=2 | Democratic | rowspan=2 align=right | Simon Cameron ! rowspan=2 | 11
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|- style="height:2em" | | rowspan=3 | 11 | rowspan=3 | Elected in 1849. | rowspan=3 nowrap | Mar 4, 1849 –Mar 3, 1855 | rowspan=3 | Whig | rowspan=3 align=right | James Cooper ! rowspan=3 | 12
|- style="height:2em" ! rowspan=4 | 12 | rowspan=4 align=left |Richard Brodhead | rowspan=4 | Democratic | rowspan=4 nowrap | Mar 4, 1851 –Mar 3, 1857 | rowspan=4 | Elected in 1851. | rowspan=4 | 12
|- style="height:2em"
|- style="height:2em" | rowspan=2 | rowspan=4 | 12 | Legislature failed to elect. | nowrap | Mar 4, 1855 –Jan 14, 1856 | colspan=3 | Vacant
|- style="height:2em" | rowspan=3 | Elected late in 1856.Retired. | rowspan=3 nowrap | Jan 14, 1856 –Mar 3, 1861 | rowspan=3 | Democratic | rowspan=3 align=right | William Bigler ! rowspan=3 | 13
|- style="height:2em" ! rowspan=2 | 13 | rowspan=2 align=left | Simon Cameron | rowspan=2 | Republican | rowspan=2 nowrap | Mar 4, 1857 –Mar 4, 1861 | rowspan=2 | Elected in 1857.Resigned to become U.S. Secretary of War. | rowspan=4 | 13
|- style="height:2em"
|- style="height:2em" | colspan=3 | Vacant | nowrap | Mar 4, 1861 –Mar 14, 1861
| rowspan=2 | rowspan=4 | 13 | rowspan=4 | Elected in 1861.Lost re-election. | rowspan=4 nowrap | Mar 4, 1861 –Mar 3, 1867 | rowspan=4 | Republican | rowspan=4 align=right | Edgar Cowan ! rowspan=4 | 14
|- style="height:2em" ! 14 | align=left | David Wilmot | | Republican | nowrap | Mar 14, 1861 –Mar 3, 1863 | Elected in 1861 to finish Cameron's term.Retired.
|- style="height:2em" ! rowspan=3 | 15 | rowspan=3 align=left | Charles R. Buckalew | rowspan=3 | Democratic | rowspan=3 nowrap | Mar 4, 1863 –Mar 3, 1869 | rowspan=3 | Elected in 1863. | rowspan=3 | 14
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|- style="height:2em" | | rowspan=3 | 14 | rowspan=3 | Elected in 1867. | rowspan=6 nowrap | Mar 4, 1867 –Mar 12, 1877 | rowspan=6 | Republican | rowspan=6 align=right | Simon Cameron ! rowspan=6 | 15
|- style="height:2em" ! rowspan=3 | 16 | rowspan=3 align=left | John Scott | rowspan=3 | Republican | rowspan=3 nowrap | Mar 4, 1869 –Mar 3, 1875 | rowspan=3 | Elected in 1869.Retired. | rowspan=3 | 15
|- style="height:2em"
|- style="height:2em" | | rowspan=5 | 15 | rowspan=3 | Re-elected in 1873.Resigned.
|- style="height:2em" ! rowspan=5 | 17 | rowspan=5 align=left | William A. Wallace | rowspan=5 | Democratic | rowspan=5 nowrap | Mar 4, 1875 –Mar 3, 1881 | rowspan=5 | Elected in 1875.Lost re-election. | rowspan=5 | 16
|- style="height:2em" | rowspan=3
|- style="height:2em"
| nowrap | Mar 12, 1877 –Mar 20, 1877 | colspan=3 | Vacant
|- style="height:2em" | Elected in 1877 to finish his father's term. | rowspan=10 nowrap | Mar 20, 1877 –Mar 3, 1897 | rowspan=10 | Republican | rowspan=10 align=right | J. Donald Cameron ! rowspan=10 | 16
|- style="height:2em" | | rowspan=3 | 16 | rowspan=3 | Re-elected in 1879.
|- style="height:2em" ! rowspan=3 | 18 | rowspan=3 align=left | John I. Mitchell | rowspan=3 | Republican | rowspan=3 nowrap | Mar 4, 1881 –Mar 3, 1887 | rowspan=3 | Elected in 1881. | rowspan=3 | 17
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|- style="height:2em" | | rowspan=3 | 17 | rowspan=3 | Re-elected in 1885.
|- style="height:2em" ! rowspan=10 | 19 | rowspan=6 align=left | Matthew Quay | rowspan=6 | Republican | rowspan=6 nowrap | Mar 4, 1887 –Mar 3, 1899 | rowspan=3 | Elected in early 1887. | rowspan=3 | 18
|- style="height:2em"
|- style="height:2em" | | rowspan=3 | 18 | rowspan=3 | Re-elected in 1891.Retired.
|- style="height:2em" | rowspan=3 | Re-elected in 1893.Legislature failed to re-elect. | rowspan=3 | 19
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|- style="height:2em" | | rowspan=4 | 19 | rowspan=4 | Elected in 1897. | rowspan=18 nowrap | Mar 4, 1897 –Dec 31, 1921 | rowspan=18 | Republican | rowspan=18 align=right | Boies Penrose ! rowspan=18 | 17
|- style="height:2em" | colspan=2 | Vacant | nowrap | Mar 4, 1899 –Jan 16, 1901 | Quay was appointed to continue the term, but the Senate rejected his appointment. | rowspan=5 | 20 | rowspan=2
|- style="height:2em" | rowspan=3 align=left | Matthew Quay | rowspan=3 | Republican | rowspan=3 nowrap | Jan 16, 1901 –May 28, 1904 | rowspan=3 | Elected late in 1901.Died.
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|- style="height:2em" | rowspan=2