REMOVE

1. trees
2. plants
3. freight cars
4. profiles (figures)

WHAT

1. banks (landforms) (1)
2. black-and-white film (1)
3. bushes (1)
4. coats (garments) (1)
5. hats (1)
6. men (male humans) (1)
7. portraits (1)
8. railroads (1)
9. rails (transit system ele … (1)
10. sky (1)
11. soil (1)
12. tools (1)
13. trains (vehicle groupings … (1)
14. utility poles (1)
15. Visual Works (hierarchy n … (1)
16. wheels (components) (1)
17. workers (1)
18. wrecks (sites) (1)

WHERE

1. New Windsor, Maryland (1)

WHO

1. Campbell, Sandra L. Still (1)
2. Clyfford Still; Still, Cl … (1)
3. Sandra L. Still Campbell; … (1)
4. Still, Clyfford (1)

More 

WHEN

1. 1969 (1)