Growing up, I assumed that the various Sioux nations were always a horse riding people. It was only later I learned that the horse was introduced to North America, and slowly adopted by some tribes for the many benefits they brought. Do native people have any stories surrounding that adoption? Any clear example of it transforming a tribal culture or art?
While not fully delving into any mythology that might have arisen from the arrival of horses into North America /u/anthropology_nerd gave a really good answer here that has a good look into the reaction of several different tribes to the early arrival of horses.