Who was the first member of the United States Senate to resign?

It was William Paterson of New Jersey, who was only the third person to vacate a seat for any reason in the United States Senate when he resigned on November 13, 1790 to become the second govenor of New Jersey. He was preceded by William Grayson of Virginia who died while holding office on March 12, 1790 and John Walker (also of Virginia) who was appointed to the post when Grayson died and held it until a successor was elected on November 9, 1790. Moses Robinson of Vermont was the 14th senator to resign.

Since there doesn't seem to be a list of U.S. Senators that have resigned anywhere (and I was bored), I compiled one here using Wikipedia - 312 total Senators with 332 resignations at the time of this post by my count. Note that this includes 3 people who were elected to the Senate but resigned prior to being seated (denoted by an asterisk).

Senate resignations by date:

William Paterson            NJ              November 13, 1790
William Samuel Johnson      CT                  March 3, 1791
Richard Lee                 VA                October 8, 1792
Charles Carroll             MD              November 30, 1792
George Read                 DE             September 18, 1793
James Monroe                VA                 March 27, 1794
John Taylor of Caroline     VA                   May 11, 1794
James Jackson               GA              November 16, 1795
Oliver Ellsworth            CT                  March 8, 1796
Rufus King                  NY                   May 23, 1796
Caleb Strong                MA                   June 1, 1796
George Cabot                MA                   June 9, 1796
Jonathan Trumbull, Jr.      CT                  June 10, 1796
Moses Robinson              VT               October 15, 1796
Richard Potts               MD               October 24, 1796
Pierce Butler               SC               October 25, 1796
Frederick Frelinghuysen     NJ              November 12, 1796
William Cocke               TN             September 26, 1797
William Bradford            RI               October ??, 1797       
Isaac Tichenor              VT               October 17, 1797
John Henry                  MD              December 10, 1797
Philip Schuyler             NY                January 3, 1798
John Vining                 DE               January 19, 1798
Andrew Jackson              TN                  April 1, 1798
John Sloss Hobart           NY                 April 16, 1798
John Hunter                 SC              November 26, 1798
John Rutherfurd             NJ               December 5, 1798
Joseph Anderson             TN                  March 3, 1799
Samuel Dexter               MA                   May 30, 1800
John Laurance               NY                 August 1, 1800
Benjamin Goodhue            MA               November 8, 1800
James Lloyd                 MD               December 1, 1800
James Schureman             NJ              February 16, 1801
Henry Latimer               DE              February 28, 1801
Ray Greene                  RI                  March 5, 1801
Charles Pinckney            SC                   June 6, 1801
Samuel Livermore            NH                  June 12, 1801
Elijah Paine                VT              September 1, 1801
John Armstrong, Jr.         NY               February 5, 1802
James Sheafe                NH                  June 14, 1802
Dwight Foster               MA                  March 2, 1803
DeWitt Clinton              NY               November 4, 1803
Theodorus Bailey            NY               January 16, 1804
John Armstrong, Jr.         NY              February 23, 1804
Abraham Venable             VA                   June 7, 1804
John Armstrong, Jr.         NY                  June 30, 1804
William Wells               DE               November 6, 1804
William Giles               VA               December 3, 1804
Andrew Moore                VA               December 3, 1804
John Breckinridge           KY                 August 7, 1805
Robert Wright               MD              November 12, 1806
John Adair                  KY              November 18, 1806
David Stone                 NC              February 17, 1807
James Fenner                RI             September ??, 1807    
Israel Smith                VT                October 1, 1807
John Smith                  OH                 April 25, 1808
John Quincy Adams           MA                   June 8, 1808
Samuel Maclay               PA                January 4, 1809
Aaron Kitchell              NJ                  March 3, 1809
Daniel Smith                TN                 March 31, 1809
John Milledge               GA              November 14, 1809
Buckner Thruston            KY              December 18, 1809
Nahum Parker                NH                   June 1, 1810
James Hillhouse             CT                  June 10, 1810
Return Meigs, Jr.           OH               December 8, 1810
Thomas Sumter               SC              December 16, 1810
Jenkin Whiteside            TN                October 8, 1811
Christopher Champlin        RI               October 12, 1811
Jean Noel Destréhan         LA                October 1, 1812
James Bayard                DE                  March 3, 1813
Dudley Chase                VT                  March 3, 1813
William Crawford            GA                 March 23, 1813
James Lloyd                 MA                    May 1, 1813
Chauncey Goodrich           CT                   May 13, 1813
George Campbell             TN              February 11, 1814
Michael Leib                PA              February 14, 1814
George Bibb                 KY                August 23, 1814
Thomas Worthington          OH               December 1, 1814
Jesse Bledsoe               KY              December 24, 1814
David Stone                 NC              December 24, 1814
William Giles               VA                  March 3, 1815
Francis Locke*              NC               December 5, 1815
William Barry               KY                    May 1, 1816
Christopher Gore            MA                   May 30, 1816
John Taylor                 SC              November ??, 1816     
William Wyatt Bibb          GA               November 9, 1816
James Turner                NC              November 21, 1816
Robert Goodloe Harper       MD               December 6, 1816
Jeremiah Mason              NH                  June 16, 1817
James Fisk                  VT                January 8, 1818
George Campbell             TN                 April 20, 1818
Eli Ashmun                  MA                   May 10, 1818
George Troup                GA             September 23, 1818
John Forsyth                GA              February 17, 1819
John Crittenden             KY                  March 3, 1819
John Eppes                  VA               December 4, 1819
Prentis Mellen              MA                   May 15, 1820
Walter Leake                MS                   May 15, 1820
William Logan               KY                   May 28, 1820
James Wilson                NJ                January 8, 1821
Freeman Walker              GA                 August 6, 1821
Harrison Gray Otis          MA                   May 30, 1822
John Williams Walker        AL              December 12, 1822
James Pleasants             VA              December 15, 1822
Caesar Rodney               DE               January 29, 1823
Samuel Southard             NJ                  March 3, 1823
James Brown                 LA              December 10, 1823
Ninian Edwards              IL                  March 3, 1824
Henry Johnson               LA                   May 27, 1824
James Barbour               VA                  March 7, 1825
David Holmes                MS             September 25, 1825
Andrew Jackson              TN               October 14, 1825
James DeWolf                RI               October 31, 1825
Edward Lloyd                MD               January 14, 1826
James Lloyd                 MA                   May 23, 1826
William Henry Harrison      OH                   May 20, 1828
Albion Parris               ME                August 26, 1828
Thomas Cobb                 GA               November 7, 1828
Nathaniel Macon             NC              December 14, 1828
Ephraim Bateman             NJ               January 12, 1829
Mahlon Dickerson            NJ               January 30, 1829
John Berrien                GA                  March 9, 1829
John Branch                 NC                  March 9, 1829
John Eaton                  TN                  March 9, 1829
Louis McLane                DE                 April 16, 1829
Edward Livingston           LA                   May 24, 1831
Issac Barnard               PA               December 6, 1831
Powhatan Ellis              MS                  July 16, 1832
Littleton Tazewell          VA                  July 16, 1832
Robert Hayne                SC              December 13, 1832
William Marcy               NY                January 1, 1833
George Troup                GA               November 8, 1833
William Rives               VA              February 22, 1834
John Forsyth                GA                  June 27, 1834
Ezekiel Chambers            MD              December 20, 1834
Peleg Sprague               ME                January 1, 1835
Charles Gayarré             LA               January ??, 1836      
John Tyler*                 VA              February 29, 1836
Ether Shepley               ME                  March 3, 1836
Willie Mangum               NC                 March 19, 1836
Isaac Hill                  NH                   May 30, 1836
Arnold Naudain              DE                  June 16, 1836
Benjamin Leigh              VA                   July 4, 1836
John Clayton                DE              December 29, 1836
Alexander Porter            LA                January 5, 1837
Richard Parker              VA                 March 13, 1837
John McKinley               AL                 April 22, 1837
John Pendleton King         GA               November 1, 1837
John Black                  MS               January 22, 1838
Felix Grundy                TN                   July 4, 1838
James Trotter               MS                  July 10, 1838
Ephraim Foster              TN                  March 3, 1839
Richard Bayard              DE             September 19, 1839
Hugh Lawson White           TN               January 13, 1840
Robert Strange              NC              November 16, 1840
Bedford Brown               NC              November 16, 1840
John Davis                  MA                January 5, 1841
Daniel Webster              MA              February 22, 1841
Clement Comer Clay          AL              November 15, 1841
Franklin Pierce             NH              February 28, 1842
Alexander Mouton            LA                  March 1, 1842
Henry Clay                  KY                 March 31, 1842
Samuel Prentiss             VT                 April 11, 1842
Samuel Southard             NJ                  June 26, 1842
Reuel Williams              ME              February 15, 1843
John Calhoun                SC                  March 3, 1843
William Sprague             RI               January 17, 1844
William King                AL                 April 15, 1844
Nathaniel Tallmadge         NY                  June 17, 1844
Silas Wright, Jr.           NY              November 26, 1844
John Berrien                GA                  March 1, 1845
Daniel Elliot Huger         SC                  March 3, 1845
Levi Woodbury               NH             September 20, 1845
William Haywood, Jr.        NC                  July 25, 1846
Walter Colquitt             GA               February 4, 1848
Ambrose Sevier              AR                 March 15, 1848
Lewis Cass                  MI                   May 29, 1848
John Crittenden             KY                  June 12, 1848
Arthur Bagby                AL                  June 16, 1848
John Clayton                DE               February 2, 1849
Reverdy Johnson             MD                  March 7, 1849
Daniel Webster              MA                  July 22, 1850
Jefferson Davis             MS             September 23, 1851
Robert Rhett                SC                    May 7, 1852
John Berrien                GA                   May 28, 1852
William King                AL              December 20, 1852
Robert Stockton             NJ               January 10, 1853
Solon Borland               AR                 April 11, 1853
Pierre Soulé                LA                 April 11, 1853
Edward Everett              MA                   June 1, 1854
Augustus Dodge              IA              February 22, 1855
Hannibal Hamlin             ME                January 7, 1857
Asa Biggs                   NC                    May 5, 1858
Hannibal Hamlin             ME               January 17, 1861
Jefferson Davis             MS               January 21, 1861
John Slidell                LA               February 4, 1861
Thomas Bragg                NC                  March 6, 1861
Salmon Chase                OH                  March 6, 1861
Thomas Clingman             NC                 March 11, 1861
Andrew Johnson              TN                  March 4, 1862
James Simmons               RI                August 15, 1862
Waitman Willey              VA                  March 3, 1863
James Bayard, Jr.           DE               January 29, 1864
William Fessenden           ME                   July 1, 1864
James Harlan                IA                   May 15, 1865
Daniel Clark                NH                  July 27, 1866
James Guthrie               KY               February 7, 1868
Reverdy Johnson             MD                  July 10, 1868
James Grimes                IA               December 6, 1869
Charles Drake               MO              December 19, 1870
William Kellogg             LA               November 1, 1872
Henry Wilson                MA                  March 3, 1873
Alexander Caldwell          KS                 March 24, 1873
Eugene Casserly             CA              November 29, 1873
Adelbert Ames               MS                January 4, 1874
Lot Morrill                 ME                   July 7, 1876
John Sherman                OH                  March 8, 1877
Isaac Christiancy           MI              February 10, 1879
John Brown Gordon           GA                   May 26, 1880
James Blaine                ME                  March 5, 1881
Samuel Kirkwood             IA                  March 7, 1881
William Windom              MN                  March 7, 1881
Thomas Platt                NY                   May 16, 1881
Roscoe Conkling             NY                   May 16, 1881
Henry Teller                CO                 April 17, 1882
Augustus Garland            AR                  March 6, 1885
Thomas Bayard               DE                  March 6, 1885
Howell Jackson              TN                 April 14, 1886
Jonathan Chace              RI                  April 9, 1889
John Carlisle               KY               February 4, 1893
Edward White                LA                 March 12, 1894
John Sherman                OH                  March 4, 1897
William Clark               MT                   May 15, 1900
Charles Fairbanks           IN                  March 3, 1905
Joseph Burton               KS                   June 4, 1906
John Colt Spooner           WI                 April 30, 1907
Philander Knox              PA                  March 4, 1909
Fountain Thompson           ND               January 31, 1910
Joseph Terrell              GA                  July 14, 1911
Joseph Weldon Bailey        TX                January 3, 1913
Warren Harding              OH               January 13, 1921
John Nugent                 ID               January 14, 1921
Albert Fall                 NM                  March 4, 1921
Josiah Wolcott              DE                   July 2, 1921
William Kenyon              IA              February 24, 1922
Truman Newberry             MI              November 18, 1922
Frank Smith                 IL               December 7, 1926
T. Coleman du Pont*         DE               December 8, 1928
Charles Curtis              KS                  March 3, 1929
Walter Evans Edge           NJ              November 21, 1929
Fred Sackett                KY                January 9, 1930
Cordell Hull                TN                  March 3, 1933
Claude Swanson              VA                  March 3, 1933
Sam Bratton                 NM                  June 24, 1933
Hugo Black                  AL                August 19, 1937
Dixie Bibb Graves           AL               January 10, 1938
A. Harry Moore              NJ               January 17, 1938
Frederick Steiwer           OR               January 31, 1938
William Gibbs McAdoo        CA               November 8, 1938
Matthew Neely               WV               January 12, 1941
John Miller                 AR                 March 31, 1941
James Byrnes                SC                   July 8, 1941
Henry Cabot Lodge, Jr.      MA               February 3, 1944
Homer Bone                  WA              November 13, 1944
Sinclair Weeks              MA              December 19, 1944
Monrad Wallgren             WA                January 9, 1945
Harry Truman                MO               January 17, 1945
Harold Burton               OH             September 30, 1945
Happy Chandler              KY               November 1, 1945
Warren Austin               VT                 August 2, 1946
Hugh Mitchell               WA              December 25, 1946
Vera Bushfield              SD              December 26, 1948
Alben Barkley               KY               January 19, 1949
Robert Wagner               NY                  June 28, 1949
J. Howard McGrath           RI                August 23, 1949
Raymond Baldwin             CT              December 16, 1949
Sheridan Downey             CA              November 30, 1950
Ralph Brewster              ME              December 31, 1952
Richard Nixon               CA                January 1, 1953
Charles Daniel              SC              December 23, 1954
Hazel Abel                  NE              December 31, 1954
Strom Thurmond              SC                  April 4, 1956
Price Daniel                TX               January 14, 1957
John F. Kennedy             MA              December 22, 1960
Lyndon Johnson              TX                January 3, 1961
Hubert Humphrey             MN              December 29, 1964
Pierre Salinger             CA              December 31, 1964
Harry Byrd                  VA              November 10, 1965
John Williams               DE              December 31, 1970
George Murphy               CA                January 2, 1971
William Saxbe               OH                January 3, 1974
Alan Bible                  NV              December 17, 1974
Wallace Bennett             UT              December 20, 1974
Howard Metzenbaum           OH              December 23, 1974
Marlow Cook                 KY              December 27, 1974
J. William Fulbright        AR              December 31, 1974
Edward Gurney               FL              December 31, 1974
Sam Ervin                   NC              December 31, 1974
Stuart Symington            MO              December 27, 1976
John Pastore                RI              December 28, 1976
Walter Mondale              MN              December 30, 1976
Paul Hatfield               MT              December 12, 1978
James Pearson               KS              December 23, 1978
Wendell Anderson            MN              December 29, 1978
Clifford Hansen             WY              December 31, 1978
Edmund Muskie               ME                    May 7, 1980
John Durkin                 NH              December 29, 1980
Richard Stone               FL              December 31, 1980
Harrison Williams           NJ                 March 11, 1982
Paul Tsongas                MA                January 2, 1985
David Karnes                NE               December 8, 1988
Dan Quayle                  IN                January 3, 1989
Gordon Humphrey             NH               December 4, 1990
Pete Wilson                 CA                January 7, 1991
Kent Conrad                 ND              December 14, 1992
Al Gore                     TN                January 2, 1993
Lloyd Bentson               TX               January 20, 1993
David Boren                 OK              December 15, 1994
Bob Packwood                OR                October 1, 1995
Bob Dole                    KS                  June 11, 1996
Frank Murkowski             AK               December 2, 2002
Jon Corzine                 NJ               January 17, 2006
Trent Lott                  MS              December 18, 2007
Barack Obama                IL              November 16, 2008
Joe Biden                   DE               January 15, 2009
Ken Salazar                 CO               January 20, 2009
Hillary Clinton             NY               January 21, 2009
Mel Martínez                FL              September 9, 2009
John Ensign                 NV                  March 3, 2011
John Kerry                  MA               February 1, 2013
Max Baucus                  MT               February 6, 2014
Tom Coburn                  OK                January 3, 2015

Interesting trivia:

• The majority of resignations were to take another political office or due to health problems.
• There are only 2 states that have never had a Senator resign - Arizona and Hawaii.
• 2 Senators have resigned on 3 separate occasions: John Armstrong, Jr. of New York and John Berrien of Georgia.
• 16 Senators have resigned on 2 separate occasions: Hannibal Hamlin of ME, George Campbell of TN, David Stone of NC, John Forsyth of GA, Daniel Webster of MA, John Crittenden of KY, Samuel Southard of NJ, Reverdy Johnson of MD, John Sherman of OH, Andrew Jackson of TN, William King of AL, James Lloyd of MA, George Troup of GA, William Giles of VA, John Clayton of DE, and Jefferson Davis of MS.
• Massachusetts has had the most resignations with 20 senators resigning a total of 22 times.
• Only 2 states have had both members of their senate delegations resign on the same day: William Giles and Andrew Moore of VA both resigned on December 3, 1804 in order to trade seats, and Thomas Platt and Roscoe Conkling of NY resigned on May 16, 1881 to protest federal patronage in New York.
• The date with the most resignations was December 31, 1974 with J. William Fulbright of AR, Edward Gurney of FL, and Sam Ervin of NC resigning.
• The year with the most resignations was 1796 with nine members resigning.
• In Delware, 4 members of the same family resigned from the U.S. Senate. James Bayard on March 3, 1813, his sons Richard Bayard on September 19, 1839 and James Bayard, Jr. on January 29, 1864, and his grandson Thomas Bayard on March 6, 1885.
• Only two people have declared independence from the Senate on July 4th - Felix Grundy of IA in 1838 and Benjamin Leigh of VA in 1836.
• 4 signers of the Constitution (William Samuel Johnson, Pierce Butler, Rufus King, and Charles Pinckney) later resigned from the Senate, as well as 4 signers of the Declaration of Independence (Charles Carroll, George Read, Richard Lee, and Thomas McKean).