Marie Railroad (MStP&SSM) (reporting mark SOO) was a Class I railroad subsidiary of the Canadian Pacific Railway in the Midwestern United States.

Commonly known since its opening in 1884 as the Soo Line[1] 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.

The Soo Line was never a major carrier of passenger traffic since its route between Chicago and Minneapolis was much longer than the competing Chicago, Milwaukee, St. Paul and Pacific Railroad (Milwaukee Road), Chicago and North Western Railway, and Chicago, Burlington and Quincy Railroad (Burlington Route) routes.

Paul, Duluth to Thief River Falls, Minnesota, and some summer-only services which relieved The Mountaineer of the local work along its route.

The Presidents of the Minneapolis, St. Paul and Sault Ste.