Glad to see people are thinking about the truly important stuff. :rolleyes:
Sometime last year, during crediting research for a card box trick, I looked into the same question.
The earliest example I found of a box resembling the ones we use today was patented on October 27, 1885 ( Patent No. 329,134
). It was invented by R. Brotz of Philadelphia and licensed to A. Dougherty for use with their decks. Pictured below is a Tally-Ho specimen from the 1890s that popped up on eBay. Photo 1 Photo 2 Photo 3
Reinhard Mller has traced the history of card boxes, concluding that they were an uncommon luxury until the late 1920s. Up to that time, cards were usually sold in paper wrappers. This may have been the case in Europe, but the text of Brotzs patent seems to indicate that by the time it was granted in 1885, the tuck flap box with thumb notch had established itself as a standard feature in the United States.
It is interesting that his box adds two slits near the opening, thus permitting the flap to fold back in such a way as to facilitate removal of the deck. We see this feature today in modern USPC boxes.
Obviously, this isnt the last word. Theres much more to discover. To be thorough, youll want to do a classification search in the USPTO and esp@ce patent databases and see if you can dig up anything older than 1885. Its a long shot, but USPC might help you. Drop them a line. You could also get in touch with a playing card collecting society. There are several out there.
So there you go. You can sleep soundly tonight knowing that at least one other person on this planet shares your curiosity. Im having a hard time believing it myself.