I've always thought that the serious collecting of postcards is actually to collect them by publisher. Furthermore, most of them are precisely numbered.
I even started classifying publishing houses and their productions, something like initial catalog.
I'm dying to watch their logos.
I would suggest starting in this thread a list of the US publishers.
Actually, I met difficulties exactly with the US cards.
Sometimes, there are three different companies marked on the back: Publisher, Producer, Distributor without specifying who is who.
Anyway, to begin with:Herbert C. Kahn Studios
, based in Yonkers, New York.
Manhattan Post Card Pub. Co.
, based in Manhattan, obviously.