 Exterior shots of the train set in the rural western U.S. were  filmed on the Canadian Pacific line from the Crowsnest Pass to  Lethbridge, Alberta. Interiors were shot in a studio, with the sets  mounted on rubber tires so they could be rocked. To simulate the  train passing through the shadow of a tree, a series of crew members  would successively move obstructions in front of each of a row of  lights shining into the windows.