| Dr. |
Baca | History professor |
| Captain |
Barger | Clive's supervisor |
| Samuel |
Baxter | Town manager |
| Dr. |
Clarke | Psychiatrist |
| Claudette |
Colbert | Actress |
| Mr. |
Colby | Mae's supervisor |
| Walter |
Cronkite | Broadcaster |
| Albert |
Einstein | Theoretical physicist |
| Enrico |
Fermi | Physicist |
| Clark |
Gable | Actor |
| Mrs. |
Galloway | Sissy's mother |
| Sylvia Jean |
Galloway | Mae's acquaintance. Aka: Sissy |
| Judy |
Garland | Actress and singer |
| Letty |
Gladding | Alleged Soviet spy |
| David |
Greenglass | Ethel's brother |
| Leslie |
Groves | Director of the Manhattan Project |
| Scotty |
Gurley | Laurel's acquaintance |
| John |
Hendrix | Author and illustrator |
| Adolf |
Hitler | Dictator of Germany |
| Mr. |
Howell | Supervisor |
| Laura |
Ingalls Wilder | American writer (reference) |
| Mrs. |
Kepple | Housemother |
| Velvet |
Maxwell | Mae's friend |
| Clive |
Morrison | Works at K-25 |
| Benito |
Mussolini | Italian politician and journalist |
| J. Robert |
Oppenheimer | Physicist, Manhattan Project leader |
| Franklin D. |
Roosevelt | 32nd U.S. President |
| Ethel |
Rosenberg | Wife of Julius, convicted spy |
| Julius |
Rosenberg | Convicted Soviet spy |
| Mr. |
Ross | Supervisor |
| Jimmy |
Stewart | Actor |
| Henry |
Stimson | U.S. Secretary of State |
| Georgeanne |
Stokes | Mae's neighbor |
| Shirley |
Temple | Actress |
| Margaret |
Thatcher | British Prime Minister (reference) |
| Prudence |
Thorpe | Dorm girl |
| Harry S. |
Truman | 33rd U.S. President |
| Elliot |
Tyson | Georgeanne's friend |
| Jonas |
Tyson | Elliot's son |
| Bobby |
Unser | Automobile racer |
| Ed |
Westcott | Photographer |
| Harris |
Willett | Mae's brother |
| Laurel |
Willett | Mae's niece |
| Maebelle Ann |
Willett | Young woman traveling to Oak Ridge. Aka: Mae |
| Granny |
Woods | Elderly neighbor |
| Garlyn |
Young | Maintenance worker |
| Amanda |
| Laurel's sister |
| Ashley |
| Elliot's daughter |
| Belle |
| Mr. Colby's daughter |
| Charlotte |
| Elliot's wife |
| Colleen |
| Sissy's friend |
| Crenshaw |
| Lieutenant Colonel |
| Dorothy |
| Mae's roommate |
| Eliza |
| Laurel's sister |
| Frank |
| Engineer |
| Hannah |
| Laurel's friend |
| Joe |
| Sylvia's brother |
| Peggy |
| Mae's dog |
| Roonie |
| Velvet's husband |
| Sallie |
| Harris's wife |
| Soda |
| Dog |
| Stanley |
| Georgeanne's husband |
| Tucker |
| Jonas's colleague |
| William |
| Garlyn's brother |
