Senate Seniority List: 115th Congress
Source: http://www.senate.gov/artandhistory/history/resources/pdf/chronlist.pdf
Senate rank is first determined by the length of consecutive service in the Senate. For senators who entered the Senate on the same day, several tie-breaking procedures determine seniority. In order of precedence, these factors are: previous Senate service, service as the vice president, previous House service; service in the Cabinet, service as a state governor. If a tie still exists, senators are ranked according to the population of their state at the time of swearing in.
| Rank | All 100 Senators | Date Service Began |
| 1 | Patrick J. Leahy, D-VT | Jan. 3, 1975 |
| 2 | Orrin G. Hatch, R-UT | Jan. 3, 1977 |
| 3 | Charles E. Grassley, R-IA | Jan. 3, 1981 |
| 4 | Mitch McConnell, R-KY | Jan. 3, 1985 |
| 5 | Richard C. Shelby, R-AL | Jan. 3, 1987 |
| 6 | John McCain, R-AZ | Jan. 3, 1987 |
| 7 | Dianne Feinstein, D-CA | Nov. 4, 1992 |
| 8 | Patty Murray, D-WA | Jan. 3, 1993 |
| 9 | James M. Inhofe, R-OK | Nov. 16, 1994 |
| 10 | Ron Wyden, D-OR | Feb. 6, 1996 |
| 11 | Pat Roberts, R-KS | Jan. 3, 1997 |
| 12 | Richard J. Durbin, D-IL | Jan. 3, 1997 |
| 13 | Jack Reed, D-RI | Jan. 3, 1997 |
| 14 | Susan Collins, R-ME | Jan. 3, 1997 |
| 15 | Michael B. Enzi, R-WY | Jan. 3, 1997 |
| 16 | Charles E. Schumer, D-NY | Jan. 3, 1999 |
| 17 | Michael D. Crapo, R-ID | Jan. 3, 1999 |
| 18 | Bill Nelson, D-FL | Jan. 3, 2001 |
| 19 | Thomas R. Carper, D-DE | Jan. 3, 2001 |
| 20 | Debbie Stabenow, D-MI | Jan. 3, 2001 |
| 21 | Maria Cantwell, D-WA | Jan. 3, 2001 |
| 22 | Lisa Murkowski, R-AK | Dec. 20, 2002 |
| 23 | Lindsey Graham, R-SC | Jan. 3, 2003 |
| 24 | Lamar Alexander, R-TN | Jan. 3, 2003 |
| 25 | John Cornyn, R-TX | Dec. 2, 2002* |
| 26 | Richard M. Burr, R-NC | Jan. 3, 2005 |
| 27 | John Thune, R-SD | Jan. 3, 2005 |
| 28 | Johnny Isakson, R-GA | Jan. 3, 2005 |
| 29 | Robert Menendez, D-NJ | Jan. 17, 2006 |
| 30 | Benjamin L. Cardin, D-MD | Jan. 3, 2007 |
| 31 | Bernie Sanders, I-VT | Jan. 3, 2007 |
| 32 | Sherrod Brown, D-OH | Jan. 3, 2007 |
| 33 | Bob Casey, D-PA | Jan. 3, 2007 |
| 34 | Bob Corker, R-TN | Jan. 3, 2007 |
| 35 | Claire McCaskill, D-MO | Jan. 3, 2007 |
| 36 | Amy Klobuchar, D-MN | Jan. 3, 2007 |
| 37 | Sheldon Whitehouse, D-RI | Jan. 3, 2007 |
| 38 | Jon Tester, D-MT | Jan. 3, 2007 |
| 39 | John A. Barrasso, R-WY | Jun. 22, 2007 |
| 40 | Roger Wicker, R-MS | Dec. 31, 2007 |
| 41 | Tom Udall, D-NM | Jan. 3, 2009 |
| 42 | Jeanne Shaheen, D-NH | Jan. 3, 2009 |
| 43 | Mark Warner, D-VA | Jan. 3, 2009 |
| 44 | Jim Risch, R-ID | Jan. 3, 2009 |
| 45 | Jeff Merkley, D-OR | Jan. 3, 2009 |
| 46 | Michael Bennet, D-CO | Jan. 22, 2009 |
| 47 | Kirsten Gillibrand, D-NY | Jan. 26, 2009** |
| 48 | Joe Manchin, D-WV | Nov. 15, 2010 |
| 49 | Chris Coons, D-DE | Nov. 15, 2010 |
| 50 | Roy Blunt, R-MO | Jan. 3, 2011 |
| 51 | Jerry Moran, R-KS | Jan. 3, 2011 |
| 52 | Rob Portman, R-OH | Jan. 3, 2011 |
| 53 | John Boozman, R-AR | Jan. 3, 2011 |
| 54 | Pat Toomey, R-PA | Jan. 3, 2011 |
| 55 | John Hoeven, R-ND | Jan. 3, 2011 |
| 56 | Marco Rubio, R-FL | Jan. 3, 2011 |
| 57 | Ron Johnson, R-WI | Jan. 3, 2011 |
| 58 | Rand Paul, R-KY | Jan. 3, 2011 |
| 59 | Richard Blumenthal, D-CT | Jan. 3, 2011 |
| 60 | Mike Lee, R-UT | Jan. 3, 2011 |
| 61 | Dean Heller, R-NV | May 9, 2011 |
| 62 | Brian Schatz, D-HI | Dec. 26, 2012 |
| 63 | Tim Scott, R-SC | Jan. 2, 2013*** |
| 64 | Tammy Baldwin, D-WI | Jan. 3, 2013 |
| 65 | Jeff Flake, R-AZ | Jan. 3, 2013 |
| 66 | Joe Donnelly, D-IN | Jan. 3, 2013 |
| 67 | Chris Murphy, D-CT | Jan. 3, 2013 |
| 68 | Mazie Hirono, D-HI | Jan. 3, 2013 |
| 69 | Martin Heinrich, D-NM | Jan. 3, 2013 |
| 70 | Angus King, I-ME | Jan. 3, 2013 |
| 71 | Tim Kaine, D-VA | Jan. 3, 2013 |
| 72 | Ted Cruz, R-TX | Jan. 3, 2013 |
| 73 | Elizabeth Warren, D-MA | Jan. 3, 2013 |
| 74 | Deb Fischer, R-NE | Jan. 3, 2013 |
| 75 | Heidi Heitkamp, D-N.D. | Jan. 3, 2013 |
| 76 | Edward Markey, D-MA | Jul. 16, 2013 |
| 77 | Cory Booker, D-NJ | Oct. 31, 2013 |
| 78 | Shelley Moore Capito, R-WV | Jan. 3, 2015 |
| 79 | Gary Peters, D-MI | Jan. 3, 2015 |
| 80 | Bill Cassidy, R-LA | Jan. 3, 2015 |
| 81 | Cory Gardner, R-CO | Jan. 3, 2015 |
| 82 | James Lankford, R-OK | Jan. 3, 2015 |
| 83 | Tom Cotton, R-AR | Jan. 3, 2015 |
| 84 | Steve Daines, R-MT | Jan. 3, 2015 |
| 85 | Mike Rounds, R-SD | Jan. 3, 2015 |
| 86 | David Perdue, R-GA | Jan. 3, 2015 |
| 87 | Thom Tillis, R-NC | Jan. 3, 2015 |
| 88 | Joni Ernst, R-IA | Jan. 3, 2015 |
| 89 | Ben Sasse, R-NE | Jan. 3, 2015 |
| 90 | Dan Sullivan, R-AK | Jan. 3, 2015 |
| 91 | Chris Van Hollen, D-MD | Jan. 3, 2017 |
| 92 | Todd Young, R-IN | Jan. 3, 2017 |
| 93 | Tammy Duckworth, D-IL | Jan. 3, 2017 |
| 94 | Maggie Hassan, D-NH | Jan. 3, 2017 |
| 95 | Kamala Harris, D-CA | Jan. 3, 2017 |
| 96 | John Kennedy, R-LA | Jan. 3, 2017 |
| 97 | Catherine Cortez Masto, D-NV | Jan. 3, 2017 |
| 98 | Tina Smith, (D-MN) | Jan. 3, 2018 |
| 99 | Doug Jones, (D-AL) | Jan. 3, 2018 |
| 100 | Cindy Hyde-Smith, (R-MS) | Apr. 9, 2018 |
* Phil Gramm resigned early, effective Nov. 30, 2002, so that John Cornyn could move into his office suite and begin organizing his staff. Cornyn did not, however, gain seniority, owing to a 1980 Rules Committee policy established by Senator Pell that no longer gave seniority to senators who entered Congress early for the purpose of gaining advantageous office space.
** Kirsten Gillibrand was appointed on January 23, 2009. She resigned her House seat on January 26, and was sworn into office on January 27, 2009.
*** Tim Scott was appointed on January 2, 2013, and resigned his House seat that same day. He was sworn into office on January 3, 2013.
