The lower falls brawny, upstream sibling, Upper Falls of the Yellowstone River makes first one then another sharp turn to negotiate a band of hard volcanic rhyolite.
While the Gibbon River originates at Grebe Lake, a stone's throw away Cascade Lake gives rise to Cascade Creek on which Crystal Falls tumbles into the Grand Canyon of the Yellowstone. So close, these two sources give their waters decidedly different paths to the Missouri River.
The reason Lower Yellowstone Falls beats Upper for greatest flowing fall in the Rockies? Cascade Creek which finds its way over the rhyolite by way of Crystal Falls.