On June 18, 1805, Clark took time out from the portage to take note of an oddity:

"We proceeded on up the river a little more than a mile to the largest fountain or spring I ever saw, and I doubt if it is not the largest in America known. This water boils up from under the rocks near the edge of the river and falls immediately into the river 8 feet, and keeps its color for half a mile which is emencely clear and of a bluish cast."

The springs were unique both in size and nature. Lewis and Clark were familiar with warm and hot springs, as they were common in Virginia. Clark's detailed description and map notations point to his naturalist's interest in the site, whereas hot springs netted only casual descriptions in his journals.

Up and down the river, Clark surveyed the largest and most beautiful falls he had ever seen. Combined with this discovery, their contributions to American science and exploration would have been considerable had they continued or not.