Visa

Headquartered in California, Visa is a financial services firm that has been around since 1958. It's become so big, in fact, six of the seven continents have Visa cardholders, which explains why it processes billions of transactions every year. Not only is it the biggest credit payment organization in the U.S., it's the second-largest financial services corporation in the world. In short, if businesses only accept one form of credit card, Visa is likely the one.