High Quality Content by WIKIPEDIA articles! The Minneapolis, St. Paul and Sault Ste. Marie Railroad (reporting mark SOO) was a Class I railroad subsidiary of the Canadian Pacific Railway in the Midwest U.S. Commonly known as the Soo Line after the phonetic spelling of Sault, it was merged with several other major CP subsidiaries on January 1, 1961 to form the Soo Line Railroad. As time passes, more and more Soo Line equipment is being repainted into the Canadian Pacific`s current paint scheme, slowly erasing the Soo`s identity as a subsidiary railroad.