Aerial photography didn't really get going until the 1920's-30's, but by the later half of the 30s, more than 2/3s of the US had been shot by aerial cameras. Three federal agencies, namely the Soil Conservation Service, Agricultural Adjustment Administration, and the Forest Service, accounted for most of the work in aerial photography. Other agencies involved in early aerial photography work included the U.S. Geological Survey, the Tennessee Valley Authority, the Coast and Geodetic Survey, and the Army Air Corps. You might check out these sources.