National Geographic : 1923 Apr
A ROTARY SNOW PLOW IN OPERATION The railroads have their hardest struggles when the heavy snows begin to fall. In the Pacific Coast mountains, snow 20feet deep on the level is not unusual. Only the big rotaries, driven by one or two big engines, will suffice to pierce the big driftsthat sofrequently occur. Sometimes ittakes 60 minutes, even with these giant machines, to go 60 feet in attacking such drifts.