My grandfather started with Southern in the 20s. Spent much of the 30s as a Fireman on the runs between Chattanooga and Kentucky. Quit Southern to work for a bridge construction company. It was more money and safer, if you can believe that. He went back to Southern in the early 60s to try to qualify for full retirement. Eventually ended up running a switcher in Chattanooga for several years. His last job was running the line he started at between Chattanooga and Kentucky. Retired sometime in the 70s.
That's pretty much all I have pieced together on his days with Southern, since he died when I was young and his second wife ended up with all of the documentation from his career.
There is a few more family story about being sent home with pay for running the switcher into a work shed by accident. Plus hitting a deaf/blind man walking on the tracks. Happened a month before he retired. He couldn't help it but always hated that.