What is the most popular breed of horse?

The American Quarter Horse

The American Quarter Horse is one of the most versatile breeds, with affinities for racing, working, and riding. The Quarter Horse outnumbers every other breed of horse in the world. With a registry of over a million registered horses he is popular everywhere. The AQHA has been registering horses since the 1940s which is a relatively short amount of time compared to the much older Arabian breed.