Besides these remains, there are numerous others in the valley of the Missouri, bearing a close resemblance to those upon the Ohio and its branches. Lewis and Clarke describe a very extensive series of works, one thousand miles up the Missouri, embracing an area of about four hundred acres. It is situated upon a peninsula formed by a bend of the river, and consists of two long walls, from six to fifteen feet in height, and from seventy-five to one hundred feet broad at the [p138] base, one of which is six thousand feet long and extends across the isthmus, the other runs along the bank of the stream. The extremity of one of the long walls terminates in a species of citadel, of semi-circular shape, which has horn-works and curtains defending the gateways, and also protected ways to the river. Here are a number of mounds and excavations similar, in all respects, to those characterizing the defensive works generally. This work is not entire, having evidently been greatly encroached upon by the river, which is constantly undermining the elevated terrace upon which it stands. Still beyond this point, upon the Platte, Kanzas, and the numerous other tributaries of the Missouri, many large and interesting works are said to occur.[96] They have been remarked high up the streams, in the valleys overlooked by the Rocky Mountains. But little more than the fact of their existence is known; of their character we are ignorant.
In the vicinity of the city of St. Louis formerly existed a very large and interesting group of works, consisting mainly of a series of mounds so arranged as to constitute the sides of a parallelogram. These mounds were generally square or oblong, with level summits. Some were terraced, bearing a close relationship to those in Mississippi and Louisiana. A few conical mounds occurred in connection with them, but there was neither embankment nor ditch. All were situated upon the second terrace.
The most interesting feature of the group is the singular work yet preserved, denominated the “Falling Garden.” This, as described by James, consists of a succession of terraces, artificially formed from the bank of the natural terrace, which is here upwards of fifty feet in height. The lowest of these terraces is eighty-seven feet broad by one hundred and fourteen long; the second is fifty-one feet, and the third thirty feet wide. Their slopes are regular, and the aspect of the structure that of a Mexican teocalli of four stages.[97]