Allis Chalmers HD38-3 tractor equipped with the 20 FT bulldozer at an earth moving job during the construction of the Garrison Dam on the Missouri River in central North Dakota, U.S. from 1947 to 1953. Ellis-Chalmers made for the construction of the Garrison Dam a special HD38 dozer, called "Siamese". It was made of two HD19 connected side to side and worked on one common bulldozer and was controlled by one person. Based on "A Big Job" Allis Chalmers promotional film.