| 100% | BYRD | 4 | Longest-serving senator in U.S. history |
| 89% | BYRD | 4 | Robert ___, longest-serving senator in U.S. history (51 years) |
| 58% | BUCHANAN | 8 | Notable lifelong bachelor in U.S. history |
| 58% | HENRYCLAY | 9 | "The Great Compromiser" in U.S. history |
| 56% | DELANO | 6 | Middle name of the longest serving US president mentioned in 6-Across |
| 54% | BERNIESANDERS | 13 | Longest-serving independent in congressional history |
| 54% | IESANDERS | 9 | Longest-serving independent in congressional history |
| 50% | TCCHEN | 6 | Scorer of the first double eagle in U.S. Open history, 1985 |
| 46% | RET | 3 | No longer in the U.S.N. |
| 46% | ERA | 3 | Reconstruction ___ (1863-1877, in US history) |
| 46% | ERAS | 4 | Long periods in history |
| 46% | ERA | 3 | Long span in history |
| 46% | ERA | 3 | Long period in history |
| 45% | GEORGEMURPHY | 12 | American actor who served as the U.S. Senator from California and was also included in the Hollywood Walk of Fame: 2 wds. |
| 45% | HURRICANE | 9 | Katrina was the costliest one in US history |
| 44% | AGO | 3 | Long ___ (way back in history) |
| 44% | ERA | 3 | ___ of Good Feelings (unity-inspired time in US history) |
| 44% | FOUNDING | 8 | __ fathers; key figures in early US history |
| 44% | ERA | 3 | Memorable, long period in history |
| 44% | ERA | 3 | Long time period in History |
| 43% | EONS | 4 | Extremely long periods in geological history |
| 42% | OLDER | 5 | Like 10-Down vis-à-vis any other senator in history |
| 42% | OLDER | 5 | Like 10-Down vis-a-vis any other senator in history |
| 42% | IMA | 3 | "___ long gone daddy in the U.S.A." (Springsteen lyric) |
| 42% | FDR | 3 | US president with the longest time in office: Abbr. |
| 41% | LAMBRUSCO | 9 | Grape, wine with long history in central Italy |
| 41% | NEVA | 4 | River in U.S.S.R. |
| 41% | ONE | 3 | Impossible score, in U.S. football |
| 41% | ONE | 3 | Impossible score in U.S. football |
| 41% | ICBM | 4 | Weapon in U.S./Russ. negotiations |