In the latter years of the 1950s, the Sioux operated a non-stop service between Chicago's Union Station and Madison, Wisconsin. On that route, the train included a dining car serving breakfast, and a first-class parlor car. West of Madison the train carried a sleeping car and coaches. West of Madison it also operated as a mail train, making frequent stops. The train crossed the Mississippi River on the Pile–Pontoon Railroad Bridge.
On October 1, 1951 the train was cut back to a Chicago to Canton, South Dakota, service with prepaid taxi connections to nearby Sioux Falls. In 1960 the train was further cut back to a Chicago to Madison coach service. The train ceased operation on May 1, 1971, when Amtrak assumed responsibility for providing a national rail service.