How did horses reach the Great Plains?

Horses reached the Great Plains primarily through trade with Spanish settlements in New Mexico and the expansion of feral herds.12

By the mid-17th century, groups such as the Southern Ute and Eastern Shoshone were among the first to obtain horses from the Spanish. These groups subsequently acted as intermediaries, facilitating the spread of horses and equestrian culture to the northern Plains. By the mid-18th century, horses had become established across the region, allowing Indigenous peoples to transition to more effective, mounted hunting of bison.312