The Lewis and Clark journal says of
the Yankton-Sioux:--

"What struck us most was an institution peculiar to them and to the Kite
(Crow) Indians further to the westward, from whom it is said to have
been copied. It is an association of the most active and brave young
men, who are bound to each other by attachment, secured by a vow, never
to retreat before any danger, or give way to their enemies. In war they
go forward without sheltering themselves behind trees, or aiding their
natural valor by any artifice. Their punctilious determination not to
be turned from their course became heroic, or ridiculous, a short time
since, when the Yanktons were crossing the Missouri on the ice. A hole
lay immediately in their course, which might easily have been avoided
by going around. This the foremost of the band disdained to do, but
went straight forward and was lost. The others would have followed his
example, but were forcibly prevented by the rest of the tribe. These
young men sit, camp, and dance together, distinct from the rest of the
nation; they are generally about thirty or thirty-five years old, and
such is the deference paid to courage that their seats in council are
superior to those of the chiefs and their persons more respected. But,
as may be supposed, such indiscreet bravery will soon diminish the
numbers of those who practise it; so that the band is now reduced to
four warriors, who were among our visitors. These were the remains of
twenty-two who composed the society not long ago; but, in a battle with
the Kite (Crow) Indians of the Black Mountains, eighteen of them were
killed, and these four were dragged from the field by their companions."

Just above the site of the city of Yankton, and near what is still known
as Bon Homme Island, Captain Clark explored a singular earth formation
in a bend of the river. This had all the appearance of an ancient
fortification, stretching across the bend and furnished with redoubts
and other features of a great fort. In the journal is given a glowing
account of the work and an elaborate map of the same. Modern research,
however, has proved that this strange arrangement of walls and parapets
is only a series of sand ridges formed by the currents of the river and
driftings of sand. Many of these so-called earthworks are situated on
the west bank of the Upper Missouri, in North Dakota and South Dakota.

A few days later, the party saw a species of animal which they described
as