Burlington introduced the vista-dome Denver Zephyr in late October, 1956, so it was an obvious candidate for a photo on the 1957 calendar. The most frequently used publicity photo of the train showed the rear end — the better to show off the dome-lounge car — with mountains in the background (courtesy of Glacier National Park) and a cowboy and cowgirl in the foreground. Perhaps to emphasize the motive power that could be used for freight as well as passenger, this photo shows the front of the train and leaves out the mountains.
Click image to download a 1.2-MB PDF of this calendar.
My copy of the calendar seems to be missing the first four months of the year, but it is plain from what we see that each month advertises a different zephyr. For May, it is the “vista-dome American Royal Zephyr.” Since Burlington had the largest fleet of streamliners in the country, it could have put different name on the page for each month of the year.