It's the company that now owns Diners Club (and is better known under that name in many countries other than the US), who in turn invented credit cards way back :)
They did not invent credit cards. Diners Club was a charge card. They did not invent that either. American Airlines had their own charge card a few decades before.
They did start the first payment card that wasn’t linked to a specific company (i.e. the American Airlines card).
The invention was having a card accepted across a wide range of merchants (all under different ownership).
Store accounts/cards have indeed been around significantly longer.
The distinction between a credit and a charge card is not that relevant in that context, in my view: For both, you spend an issuer’s money at unaffiliated merchants and pay the issuer back later.
