The Spokane, Portland & Seattle owned two steel heavyweight solarium-observation cars with extra-large windows in the rear rather than a rear platform, as SP&S trains went too fast (79 mph) for passengers to be safe or comfortable on an open platform. Each car had eight sections (sixteen beds), a small buffet for evening drinks and morning coffee, and a lounge. Sleeping car passengers could board the car in Spokane before the rest of their train arrived from the east, thus avoiding the stress of sitting in a waiting room. The solarium room was more for show than actual use as the trains traveled in darkness for almost their entire trip, even in summer.
Pullman built the cars in 1926 for use on Rock Island trains under the names Des Moines Club and Omaha Club. In 1940, GN and NP each purchased one of the cars for use on the Portland sections of the Empire Builder and North Coast Limited. In 1949, the railways formally sold the cars to SP&S to serve trains 3 & 4, the Portland connections to the Oriental Limited (later Western Star) and Alaskan (later Mainstreeter. At that time, SP&S renamed the cars Mount Adams and Mount Jefferson.