REMOVE

1. trees
2. sky
3. railroads
4. workers
5. 1969

WHAT

1. Visual Works (hierarchy n … (1)
2. arcades (structural assem … (1)
3. black-and-white film (1)
4. buildings (structures) (1)
5. cabins (houses) (1)

More 

WHERE

1. Lake Louise, Alberta, Can … (1)

WHO

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

WHEN

1. 1929 (1)
2. 1940 (1)
3. circa 1930 July 16 (1)