Just as an FYI...
The 9mm Steyr, circa 1912, and the 9mm Largo, circa 1921 (And I think before as the 9mm Bergmann-Bayard.) bark right on the heels of, or surpass slightly the .38 Super. Perhaps we should qualify it as "the most powerful domestic pistol cartridge until the advent of the .357 Mag."
Then of course, there's the 9mm Mauser Export of Broomhandle chambering. I'm not sure when exactly this number came about, but it enjoyed a resurgence of interest in the '20's, so I imagine it predates THAT time slot. It never caught on here, as a 9mm x 25mm case (The 7.62 x 25 necked up to 9mm.) running 125's at some 1400-ish fps doesn't fit through anything but a Broomhandle Mauser.
That's a hot one. Naturally I want one, but they are rare unto ridiculous.
Sounds like a good prospect for a mag-length revolver cylinder 'n moonies, though.
Additional: I thought the .38 Super came about because .45's don't punch through car bodies too well.