REMOVE

1. railroads
2. plants
3. automobiles
4. trees
5. trains (vehicle groupings)

WHAT

1. Visual Works (hierarchy n … (1)
2. black-and-white film (1)
3. chairs (furniture forms) (1)
4. curators (1)
5. doors (1)

More 

WHERE

1. Ensenada, Baja California … (1)

WHO

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

WHEN

1. 1949 (1)