The four-horse chariot was introduced in 680 BC as the first equestrian event. In 384 BC, the four-horse chariot race for foals was added. At Olympia the horses ran twelve rounds, that is about 14 km. The foals ran only 8 rounds or 9 km.
Also after the introduction of the races of two-horse chariots and horses with rider, the four-horse chariot remained the most prestigious event, because putting together a good team of four horses demands more money and effort than a smaller team. Pindar has written as many as fourteen odes for victors of the four-horse chariot race (against eight for the pankration, the second most frequent sport).
The two middle horses were harnessed under the yoke, the two outer horses were attached to it with a rope. The right outer horse was the most important: since the turns were always taken left, the right horse had to be the fastest.