I've heard a similar tale about a bluff on the Susquehanna River near Pittston, PA. I forget the name of the ridge, but the legend was that someone being chased by Indians made the jump with his horse, and survived, and the ridge was named after him. The river's not directly below, but this is explained to children: "back then, the river ran right below." I forget what the explanation was regarding getting a horse to jump off of a cliff.