Hello T-Joe,
My Speer Reloading Manual number 13 gives brief histories of each cartridge before the recipes of those caliber-cartridges.
"The 38 Special was introduced by Smith & Wesson in 1902 as a ballistic improvement over the 38 Long Colt cartridge." I do not know if the 38 Long Colt is the same as the 38 S&W aka: "38 Colt New Police, the 38 Super Police, and 38/200". This Speer Manual does not recipe the 38 Long Colt.
38 Special +P introduced by S&W in the early 1930's, then 357 Mag in 1935 with S&W's 38 Special +P research and Elmer Kieth with Phil Sharpe inspiring heavy encouragement and development. {per Speer Reloading Manual number 13}
Yeti76620