On the other hand, a large amount of mileage was spun off in 1987 to Wisconsin Central Ltd., now part of the Canadian National Railway.

Surface Transportation Board groups all of the company's U.S. subsidiaries under the Soo Line name for reporting purposes.

Major branches include a connection from the border at Noyes, Minnesota, to Glenwood and, until it was sold to the Indiana Rail Road in 1983, a line from Chicago to Louisville, Kentucky.

The Soo Line gained control of the Minneapolis, Northfield and Southern Railway (MNS), a Twin Cities–area shortline railroad, in June 1982.

The Soo Line's last passenger train was the Copper Country Limited, a joint service with the Milwaukee Road inherited from the Duluth, South Shore and Atlantic.

Unable to implement its proposed labor rule changes, the Soo Line sold the approximately 2,000-mile (3,200 km) LSTD to a new regional railroad, Wisconsin Central Ltd., in 1987 for $133 million.

In 1990, CP gained full control of the Soo Line Corporation, of which it had previously owned about 56% of the common stock.