REMOVE

1. rubbish
2. yards (areas)
3. coats (garments)
4. sky
5. clouds
6. buildings (structures)

WHAT

1. Visual Works (hierarchy n … (1)
2. artists (visual artists) (1)
3. black-and-white film (1)
4. bushes (1)

More 

WHERE

1. Westminster, Maryland (1)

WHEN

1. 1961 (1)
2. after 1961 (1)