Standardbred horse or trotter, American breed of light horse developed especially for harness, or sulky, racing. Of Thoroughbred ancestry, it is similar in appearance to a thoroughbred but has shorter legs. The breed is characterized by great stamina and its ability to trot or pace at extreme speeds without breaking into a running gallop. Sulky racing originated in the United States on the dirt roads of the early 19th cent., but it has since spread, as has the horse which made it possible, to Europe, Australia, Japan, and New Zealand. Standardbreds are any color, usually chestnut, black, or brown; they average 15 hands (60 in./160 cm) in height and weigh near 1,000 lb (450 kg).