overed and described by Lewis and Clark:

"This river is three hundred yards wide at the point where it
receives the waters of Medicine (Sun) River, which is one hundred and
thirty-seven yards in width. The united current continues three hundred
and twenty-eight poles to a small rapid on the north side, from which it
gradually widens to fourteen hundred yards, and at the distance of five
hundred and forty-eight poles reaches the head of the rapids, narrowing
as it approaches them. Here the hills on the north, which had withdrawn
from the bank, closely border the river, which, for the space of three
hundred and twenty poles, makes its way over the rocks, with a descent
of thirty feet. In this course the current is contracted to five hundred
and eighty yards, and after throwing itself over a small pitch of five
feet, forms a beautiful cascade of twenty-six feet five inches; this
does not, however, fall immediately or perpendicularly, being stopped by
a part of the rock, which projects at about one-third of the distance.
After descending this fall, and passing the cottonwood island on which
the eagle has fixed her nest, the river goes on for five hundred and
thirty-two poles over rapids and little falls, the estimated descent
of which is thirteen and one-half feet, till it is joined by a large
fountain boiling up underneath the rocks near the edge of the river,
into which it falls with a cascade of eight feet. The water of this
fountain is of the most perfect clearness, and of rather a bluish cast;
and, even after falling into the Missouri, it preserves its color
for half a mile. From the fountain the river descends with increased
rapidity for the distance of two hundred and fourteen poles, during
which the estimated descent is five feet; and from this, for a distance
of one hundred and thirty-five poles, it descends fourteen feet seven
inches, including a perpendicular fall of six feet seven inches.
The Missouri has now become pressed into a space of four hundred and
seventy-three yards, and here forms a grand cataract, by falling over
a plain rock the whole distance across the river, to the depth of
forty-seven feet eight inches. After recovering itself, it then proceeds
with an estimated descent of three feet, till, at the distance of
one hundred and two poles, it is precipitated down the Crooked Falls
nineteen feet perpendicular. Below this, at the mouth of a deep ravine,
is a fall of five feet; after which, for the dis