The C&S did not have any O1a's. They did have O1's, an earlier Burlington design dating back to 1910-1911, and with lower drivers on the C&S only, of 57".
The C&S received a group of 6 Burlington heavy USRA 2-8-2's in 1957, to supplement their motive power needs. Those locomotives were the last steam locomotives sold for regular service in the United States. The USRA locomotives were renumbered into the C&S numbering scheme (#'s 804-809).
The leased O1a's on the Colorado & Southern ran from Denver to Fort Collins and most of the intermediate branch lines, 1958-1959. Some of them were Elesco-equipped, including #4978, now on display in Mendota, IL.
