This Milwaukee Road note page says, “Route of the Super Dome Hiawathas and Western ‘Cities’ Streamliners.” This dates it to later than October 30, 1955, when Union Pacific shifted its passenger trains from the C&NW to the Milwaukee for their Chicago-Omaha leg. The mountains in the background of the image suggests it is before 1961, when the Milwaukee terminated the Olympian Hiawatha to Seattle.
This is one of the rare note pads that emphasizes passenger trains without mentioning freight. Since the railroads distributed note pads mainly to shippers, they usually used them to advertise their freight service as well as trains passenger trains. Since I prefer to collect passenger-related items, the passenger-only note pads in my collection is probably not representative of all note pads the railroads printed.