If you have the magazine page in front of you, as I do, it's easy to see where the idea for the cover story of Captain Marvel Jr #114 (1952) came from.
An illustration for the Association of American Railroads provided the inspiration. My copy of the ad is from the April 28, 1947 issue of Life magazine.Ideas have to come from somewhere. I think this ad, which might have come from a stack of magazines at the writer's house, was a springboard for a story.
The Grand Comics Database credits Bud Thompson with the cover, and Joe Certa with pencils and inks on “The Train That Traveled Through Space.”