This looks like a poster but it is actually the top of a calendar. Unfortunately, someone cut the bottom off before I acquired it. The calendar is presumably for 1953, the year the Super Domes first appeared on the Hiawathas.
The artwork is signed “Addison,” which refers to Robert Addison, who did both fine art and commercial art. Born in Boise, Idaho in 1924, Addison studied at the Chicago Art Institute and continued to live in Chicago for most of his life. In fact, his fine art, which includes many cityscapes, is called “Chicago realism.” His commercial clients included the Pennsylvania Railroad, Pan AM, TWA, Ford, and Chevrolet.
Although the calendar just refers to the Hiawathas, this illustration is clearly the Olympian Hiawatha going through Sixteen Mile Canyon in Montana. The railroad purchased enough Super Domes to operate on both the morning and afternoon Hiawathas between Chicago and the Twin Cities as well as the Olympian Hiawatha. Although Milwaukie illustrators always liked to include a pretty girl waving at the train, Sixteen Mile Canyon was actually pretty hard to reach, especially since it was all on private land.