The top is a smooth level plain.

The journal says:-- "The Indians have made it a great article of their superstition: it is called the Mountain of Little People, or Little Spirits; and they believe that it is the abode of little devils, in the human form, of about eighteen inches high, and with remarkably large heads; they are armed with sharp arrows, with which they are very skilful, and are always on the watch to kill those who should have the hardihood to approach their residence.

The tradition is, that many have suffered from these little evil spirits, and, among others, three Maha Indians fell a sacrifice to them a few years since.

This has inspired all the neighboring nations, Sioux, Mahas, and Ottoes, with such terror, that no consideration could tempt them to visit the hill.

We saw none of these wicked little spirits, nor any place for them, except some small holes scattered over the top; we were happy enough to escape their vengeance, though we remained some time on the mound to enjoy the delightful prospect of the plain, which spreads itself out till the eye rests upon the northwest hills at a great distance, and those of the northeast, still farther off, enlivened by large herds of buffalo feeding at a distance." The present residents of the region, South Dakota, have preserved the Indian tradition, and Spirit Mound may be seen on modern maps of that country.
Passing on their way up the Missouri, the explorers found several kinds of delicious wild plums and vast quantities of grapes; and here, too, they passed the mouth of the Yankton River, now known as the Dakota, at the mouth of which is the modern city of Yankton, South Dakota.