Marshall is a self-propelled Canadian snowplough locomotive, who works in the Canadian Rockies.
Marshall was ploughing snow through the Rocky Mountains when he came across Thomas, who was stranded in a snowdrift. Thomas thought that Marshall was a monster at first, but Marshall introduced himself and showed Thomas his rotary snowplough. Marshall then had Thomas back out onto his line while Marshall travelled in front, allowing Thomas to pass through the mountains safely.
Marshall is based on Colorado & Southern Rotary Steam Snow Plow No. 99201, built by the Cooke Locomotive and Machine Works in 1899. This plow operated over a number of Colorado mountain lines from 1899 until 1965. It was donated to the Colorado Railroad Museum in 1972. However, Marshall is self-propelled, whereas his basis is not.
Marshall is painted dark grey with a dark red rotary snowplough and red lining. The number "64" and the Canadian flag are painted on the sides of his cab.