The Shoshone or Shoshoni were characterized by nomadic groups that took their culture from the earlier Bitterroot culture and Great Basin tribes that migrated north via the Owyhee River. They were the most powerful tribe in the Rocky Mountains area, and were known to many Great Plains tribes as the Snakes. In the 18th century, Shoshone territory extended beyond the Snake River Plain, extending over the Continental Divide into the upper Missouri River watershed and even further north into Canada. A smallpox epidemic brought by European explorers and fur trappers was responsible for wiping out much of the Shoshone east of the Rocky Mountains, but the Shoshone continued to occupy the Snake River Plain. Eventually, the Shoshone culture merged with that of the Paiute and Bannock tribes, which came from the Great Basin and the Hells Canyon area, respectively. The Bannock brought with them the skill of buffalo hunting and horses they had acquired from Europeans, changing the Shoshone way of life significantly.