I have always wondered if the song was out my hometown, since there are 38 or 39 states with Clarksville. Then I read that the song is from the Vietnam war era when so many had to go to nearby Fort Cambbell, Ky and many caught the train from Downtown Clarksville to Fort Campbell.
BTW I only live a couple of miles from gate 1 at Fort Campbell, but 5 miles from the main gate