REMOVE

1. workers
2. scaffolds
3. silver gelatin

WHAT

1. Grand Coulee Dam (dam) (2)
2. Visual Works (hierarchy n … (2)
3. banks (landforms) (2)
4. construction sites (2)
5. cranes (equipment) (2)

More 

WHERE

1. Grand Coulee, Washington (2)

WHO

1. Clyfford Still; Still, Cl … (2)
2. Still, Clyfford (2)

WHEN

1. 1936 (2)
2. 1937 (2)
3. circa 1936 to 1937 (2)