TOD
I can name my three earliest known classical conductors:
Stokowski, from my having seen FANTASIA at an early age.
Bernstein, likely due to his television work, though I'd have to look up dates to see where all of that falls.
Emerson Buckley, as conductor of the local (Fort Lauderdale) symphony.
We had some classical records in the house but they weren't bought because of any conductor. By the time I was buying my own records, Ormandy, Reiner, Leinsdorf and Fiedler were my known ones. I don't think I was much aware of Szell before heading up to school in Cleveland. Also, Isidore Godfrey from D'Oyly Carte recordings. He was just a name, but I was aware.
As for popular music or Broadway, I don't really have a clue from my early years. Maybe someone will jog my memory in that department.