REMOVE

1. hats
2. sky
3. buildings (structures)
4. rubbish
5. farmhouses
6. bushes
7. windows

WHAT

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

More 

WHERE

1. Westminster, Maryland (1)

WHEN

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