Eisenhower, 1950's. Former General of the Allied forces in WWII. A great American.
Well, yeah, sorta -- but he did "hold office" in the U. S. government. That's why he was called an Army OFFICER.
So to find a POTUS who never held any kind of public office, we gotta go all the way back to Woodrow Wilson -- truly one of the worst men ever to wear the Presidential mantle.