REMOVE

1. sky
2. hats
3. clouds
4. trees
5. rubbish
6. yards (areas)

WHAT

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

More 

WHERE

1. Westminster, Maryland (1)

WHEN

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