The Appaloosa is a horse breed known for its preferred leopard-spotted coat pattern and other distinctive physical characteristics. The American breed was developed by the Nez Perce people of the American Pacific Northwest. The Nez Perce people lost most of their horses following the end of the Nez Perce War in 1877 and the breed fell into decline for several decades. However, a small number of dedicated breeders kept the Appaloosa alive for several decades until a registry was formed in 1938. Today the Appaloosa is one of the most popular breeds in the United States, and it was named the official state horse of Idaho in 1975.
The Appaloosa is best known as a stock horse used in a number of western riding disciplines, but is also a versatile breed with representatives seen in many other types of equestrian activity. The color pattern of the Appaloosa is of great interest to those who study equine coat color genetics, as both the coat pattern and several other physical characteristics are linked to the "Lp" or "leopard" gene or gene complex, but the precise inheritance mechanism is not fully understood. The Appaloosa has influenced many other horse breeds, including several gaited horse breeds.