The short version The archive turns up 107 records, most of them around Grand Canyon. 2 are confidently dated; the other 105 are educated guesses — about as precise as it sounds. All are free to use.
Aerial View of Shallow Reef or Sandbar, Tropical Waters
1940–1970
Aerial View of Volcanic Island with Steam Plumes, Mid-20th Century
1940–1960
Mountain Valley in Mist, Early Color Photography
1940–1960
Desert Wildflower, High Desert Plateau Region
c. 1949
Open-Pit Mine Workings and Waste Dumps, Western North America, 1940s
1940–1949
Arctic Research Station, Boreal Forest in Winter Snow
1945–1965
Mountain Lake at Dusk, Mid-20th Century
1940–1965
Mountain stream in winter, Pacific Northwest evergreen forest
c. 1940
River at Dusk, American South, 1940s–1950s
1940–1955
Rural Landscape at Sunset with Power Lines, circa 1940s
1945–1949
Quarry or Excavation Site with Workers, mid-20th Century
1940–1965
certain
inferred
low confidence