River Sub is an almost 124 miles long railway network that spreads from La Crescent to Saint Paul, Minnesota. Soo Line Railroad, a subsidiary of Canadian Pacific Railway, operates the line that runs along the Mississippi River. The network was started in 1865 when Minnesota & Pacific Railroad Company built a line from Saint Paul. The line is usually used by the passenger trains but Milwaukee Road's Hiawatha is one of the most renowned trains use the lines since 1935. To offer more safety and security to the passengers as well as high speed, automatic cab signaling was installed in the route in 1920s or 1930s.