REMOVE

1. trucks
2. sky
3. soil
4. houses
5. railroads

WHAT

1. Visual works (hierarchy n … (2)
2. blue (2)
3. brown (2)
4. farming (2)
5. farms (2)

More 

WHERE

1. Bow Island, Alberta, Cana … (1)
2. Pullman, Washington (1)

WHO

1. Still, Clyfford (2)

WHEN

1. 1925 (1)
2. 1935 (1)