While you’re thinking about movie ads for the 50’s, don’t forget Forbidden Planet, East of Eden, Ben Hur, Giant, From Here to Eternity and On the Waterfront to name a few. I found a doozy of a website for vintage ads: adclassix.com
Think about the exact year and there may be a way to identify it.
For example: My Conemaugh Road & Traction is set to peg in the year 1956. So, the scenery is leaning toward fall foliage to back up the billboards because President Eisenhower is up for re-election, and; there willl be an “I Like Ike” billboard or two. I’m also planning on a billboard ad for the tv show, “Howdy Doody,” which is very 1950s.
A way to get an exact year is to locate a Ford or Chevy ad. Did you know that Greyhound Scenicruisers came out in the mid-1950s?
Don’t forget that many railroads were still into heavy advertising like for passenger service. Put your favorite roadname into an eBay search, and you’ll come up with pictures of posters and postcards.
In addition to Google Images, here is another good starter at http://en.wikipedia.org/
Can’t forget Mail Pouch chew.