I always thought they were a rail carrier now rolled up into Burlington Northern.
(Though I do know something about the song—there’s a radio station in Dallas that plays classic rock)
You are both correct, a railroad, and a Youtube classic:
https://www.youtube.com/results?search_query=atchison+topkeka+and+the+santa+fe
I like the one with Judy Garland’s album cover. Man, did she look hot ! Thanks, to both:)