These were solved by NPL members Bartok, Ember, Kea, Lilith, Qaqaq, Rebel, Saxifrage, Treesong and Wrybosh.  NPL member Treesong put them all together.
1. Only 20th century, not killed, not a president, not on US currency (remember the Kennedy half) and not three syllables.
2. Not Spanish-speaking, not in northern hemisphere and doesn't end in A, not continental, doesn't start with C.
3. Doesn't end /oo/, doesn't end in 'w' and not a verb, not three letters, not C+V and the only noun.
4. Capitalized, doesn't end in 'u', not three letters, not /loo/.
5. Doesn't end /ik/, not two syllables, not an adjective, not five letters.
6. Doesn't start 'a', not one word, not a place name, not a movie.
7. Edible part not aboveground and doesn't end in 'e', no double letter and only one starting with a vowel, not a vegetable, not
six letters.
8. Doesn't end in 'th', not five letters, only one with a repeated letter, doesn't start 'f'.
9. Not two words, not male, not a poet, not American.
10. Not gray, not solid, not a metal, not an element.
11. Not an animal, doesn't start with 'c' and contains no a', not five letters, doesn't end with another word.
12. Extinct, not one word, smaller than a breadbox, herbivore.
13. Not male, not gay, not a performer and not alive, not American and titled.
14. Not a professional musician, no royalty in name, not male, no card in name.
15. Doesn't start with 'n', only city, not US, no coastline and not eastern.