The water comes from underground springs above and at the falls, and provides an almost constant flow rate of 100 million gallons a day, even during the dry summer months.
The falls are an example of river drainage regulated by stratigraphically-controlled springs, and also of a waterfall formed by undercutting of horizontal rock layers.
The falls were called "the Eighth Wonder of the World" by President Theodore Roosevelt, and were declared a National Natural Landmark in December 1984.