The old Southern Railway was one of the first major US railroads to make the switch from steam-powered locomotives to diesel locomotives, beginning in the early 1940s.
By the end of the end of the 1950s, diesel had all but replaced steam across the US. Southern, recognizing that there was no longer a need for railroad firemen, had stopped hiring them.
This was a revolutionary concept. Firemen had been around almost since the beginning of railroads more than a century earlier, with the most notable duties being maintaining fires and steam pressure in steam locomotives.
But as diesel locomotives required no fire, many of the fireman’s duties were no longer needed.