In 1949, businessman Frank McNamara was about to pay for dinner when he realized something terrible.
He'd forgotten his wallet.
While this scenario isn't that uncommon, McNamara's response was determined to ensure he'd never be caught without cash again, he invented the Diners Club card — a wallet-sized piece of cardboard that allowed carriers to dine at associated restaurants and settle their bills at the end of each month.
McNamara wasn't the first person to codify the IOU.
There's evidence of deferred payment systems stretching all the way back to ancient Mesopotamia.
In America's Wild West, ranchers and farmers used metal plates as credit placeholders.
And just a few years before McNamara's dining disaster, many department stores and airlines had already begun rolling out reward programs and charge cards.
But the Diners Club card was different.
Where previous credit arrangements saw one business authorizing credit for one individual, McNamara's card gave users credit with over two dozen otherwise unassociated businesses.
This decentralized credit was revolutionary, and in just one year, the Diners Club card gained 10,000 users.
