Onawa was a human woman who is now a ghost.
The last survivor of a local native tribe slaughtered by the earliest Western settlers to the Big Thunder Mountain region, Onawa, then a very young child, had been taken in by a kind-hearted man who may or may not have been a younger Barnabas T. Bullion, eventually becoming Bullion's maid. By the late 1870's however, Onawa had grown up into a fierce and resentful markswoman, who lived a double life as one of Jason Chandler, Jr's gang of Robin Hood-esque outlaws. She was eventually murdered by George Willikers as the vile man's last villainous deed even as he plummeted to his death. However, having died within Big Thunder Mountain and in the process of protecting it, Onawa was resurrected by the Thunderbird as a spirit loyal to it.
Behind the scenes
Onawa appears in the the Big Thunder Mountain Railroad comic printed in 2015 as part of the Disney Kingdoms event.