REMOVE

1. mountains
2. barriers
3. rubbish
4. rivers
5. boys
6. Grand Coulee, Washington

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)

WHO

1. Campbell, Sandra L. Still (1)
2. Sandra L. Still Campbell; … (1)

WHEN

1. 1964 (1)