| Answer | Crossword Clue |
|---|---|
| ASTOR | One of "the 400" |
| ASTOR | One of the 400 |
| ASTOR | One of the 400. |
| YMCA | One of 2,400-plus in the U.S. |
| ATM | One of 400,000-plus in the U.S. |
| SMITH | One of about 2,400,000 in the United States |
| CLAM | Ming, the oldest animal ever discovered (400+ years), was one |
| ATOMIST | Democritus was one, circa 400 B.C. |
