Strom Thurmond, Democrat and then Republican, South Carolina 100
Theodore F. Green, Democrat, Rhode Island 93
Robert Byrd, Democrat, West Virginia 92
Carl Hayden, Democrat, Arizona 91
Additionally, the potential future shows the following:
Dianne Feinstein, Democrat, California, would reach age 90 in next term ending 2024 with her reaching that age in 2023, with her victory in November for another six year term assured.
Chuck Grassley, Republican, Iowa, would reach age 90 in 2023 if he won another term in 2022.
Richard Shelby, Democrat and then Republican, Alabama, would reach age 90 in 2024, if he won another term in 2022.
James Inhofe, Republican, Oklahoma, would reach age 90 in 2024, if he won another term in 2020.
Pat Roberts, Republican, Kansas, would reach age 90 in 2026, if he won another term in 2020.
The question is whether it is good for the nation to have five Octogenarians in the US Senate in 2019, and this after John McCain died and Orrin Hatch is retiring.
It is, however, a growing trend, and the present Democratic leadership in the House of Representatives (Nancy Pelosi, Steny Hoyer, and James Clyburn), all will reach 80 soon, with Pelosi reaching 80 in March 2020, Hoyer reaching 80 in June 2019, and Clyburn reaching 80 in July 2020, so all age 80 during the 116th Congress.
The debate will grow over the aging of Congress, and particularly of leadership and influence over the future of American democracy.