REMOVE

1. plants
2. sky
3. coats (garments)
4. clouds
5. rubbish
6. black-and-white film

WHAT

1. Visual Works (hierarchy n … (1)
2. artists (visual artists) (1)
3. buildings (structures) (1)
4. bushes (1)

More 

WHERE

1. Westminster, Maryland (1)

WHEN

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