REMOVE

1. rock
2. trees
3. sky
4. barriers
5. hills
6. mountains
7. machinery
8. buildings (structures)

WHAT

1. Visual Works (hierarchy n … (1)
2. automobiles (1)
3. black-and-white film (1)
4. bushes (1)
5. daughters (1)

More 

WHERE

1. Westminster, Maryland (1)

WHO

1. Clyfford Still; Still, Cl … (1)
2. Still, Clyfford (1)

WHEN

1. 1966 (1)
2. ca. 1966 (1)