REMOVE

1. trees
2. garages
3. roads
4. rubbish
5. freight cars
6. fields (land)

WHAT

1. Visual Works (hierarchy n … (1)
2. beaches (1)
3. black-and-white film (1)
4. buildings (structures) (1)
5. bushes (1)

More 

WHERE

1. Ensenada, Baja California … (1)

WHO

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

WHEN

1. 1949 (1)