Mr. H. M. Brackenridge, writing in the year 1811, says: "I have frequently examined the mounds at St. Louis. They are situated on the second bank, just above the town, and disposed in a singular manner; there are nine in all, and form the three sides of a parallelogram, the open side towards the country being protected, however, by three smaller mounds, placed in a circular manner. The space inclosed is about three hundred yards in length and two hundred in breadth. About six hundred yards above these is a single mound, with a broad stage on the river side ; it is thirty feet in height, and one hundred and fifty in length ; the top is a mere ridge of five or six feet wide. Below the first mounds there is a curious work called the Falling Garden. Advantage is taken of the second bank, nearly fifty feet in height at this place, and three regular stages or steps are formed by earth brought from a distance. This work is much admired—it suggests the idea of a place of assembly for the purpose of counselling on public occasions."
     Accompanying the foregoing description is a simple diagram which, as it does not seem to be the result of any actual survey, and therefore of no scientific value, need not be reproduced in this connection.
     Dr. Beck, who noticed them twelve years afterwards, presents in his work another diagram, which seems to have been the result of more careful observation, although in this, however, one of the nine, and the three smaller mounds described by Mr. Brackenridge as protecting the side of the parallelogram opening towards the country, are wanting. From all the information I can gather, I believe the following plan will present the true relation of the mounds here described :      

     One of the above group undoubtedly represents the old landmark known as the Big Mound, ( a representation of which as it appeared at the time of its removal, faces the first page of the present volume), which once stood at the corner of Mound street and Broadway, but which was entirely demolished in 1869. This I suppose to have been the terraced mound, represented by Mr. Brackenridge to have been located six hundred yards north of the main group. The Big Mound is known to have been beautifully terraced, and nothing of the kind is mentioned in connection with those constituting the parallelogram. Nor is the Falling Garden spoken of as a mound, but only as a terraced bank. For these and other reasons which need not be dwelt upon, after much reflection, I am persuaded that the terraced mound, afterwards known as the Big Mound, was the last to disappear before the encroachments of the rapidly-growing city. Be this as it may, this most interesting work will be particularly described under the more appropriate head of Sepulchral Caverns, when I shall be able to speak with more confidence, as I shall give there the result of my own observations. There were formerly many other mounds in the immediate vicinity of St. Louis, rivaling in magnitude and interest those described by the authors just quoted, but which escaped their notice In fact, the second terrace of the Mississippi, upon almost every available commanding point of elevation, was finished with them. Nineteen years ago, in a conversation with the late Col. John O'Fallon, he informed me that his family residence on the Bellefontaine road was erected upon one of those ancient mounds. It must have been very large, although I do not recall the dimensions. He stated, further, that as the summit was being leveled, preparatory to building, human bones by the cart-load were disclosed, along with stone axes and arrowheads and the like, without number. He then led me to the forest west of his dwelling, and called my attention to the small hillocks which abounded there in prodigious numbers, which he conjectured were the residence sites of former inhabitants, because of their regularity, and from the fact that upon excavating them they disclosed ashes and charcoal.
     Still farther north, upon the highest points of the second terrace, I have traced the remains of others which must have been quite imposing before they were subjected to the leveling influence of agriculture. In Forest Park, a few miles west of the city, there is a small group of mounds which the park commissioners, I am happy to know, have resolved to preserve. It is a pity that none of the larger ones have been spared, to stand hereafter as the memorials of a people whose origin is hid in the night of oblivion. But let them remain, such as they are, and when future generations shall throng the green groves and shady walks of that beautiful garden of their great city, these shall recall the fainting echoes of another race, whose homes once clustered, in days long gone, upon the banks of that great river where a statelier—can we say happier —city stands to-day.
     The works thus briefly noticed are only a few of the great group of large circumference, of which that king of mounds, on the fertile plains across the river, known as Monk's Mound, was the radiating center. That high place was a temple mound—the holy mountain for this whole region, doubtless,—and the smoke which ascended from the perpetual fire of its sacred altar could be seen for many miles on every side.
     But while our business now is with the ancient people of Missouri, it should be borne in mind that the imaginary lines which divide us into States had no existence in those other times, when a mighty people dwelt upon either side of the Mississippi, outnumbering far, perhaps, the present occupants; who were homogeneous in their commercial pursuits, arts and worship. They traded with the nations who dwelt by the sea, and brought from thence the shells and pearls of the ocean, and left them in their tombs, along with the precious wares of their own handicraft, for our admiration and instruction.

But before we leave St. Louis, another work demands a notice, which the following (Fig. 9), will illustrate.

This class of works appears frequently in Iowa, but was formerly found in greatest numbers in Missouri. The one figured here was located on Root River, about twenty miles west of the Mississippi. The central mound is represented as being thirty-six feet in diameter, and twelve feet in height. The circle inclosing it was nearly obliterated. The long embankments which form the sides of the triangle were each one hundred and forty-four feet in length, and respectively three, four and five feet in height, and twelve feet in diameter; and what is singular, the sum of the heights of the embankments equals the vertical height of the central mound, and these two amounts multiplied together, give the exact length of the embankments. Sometimes works of this description are built in the form of a square, with four embankments; but of whatever form, it is stated that the same relation of the sum of the heights of all the embankments to the height of the central mound is always presented, and the product of these gives the length of the embankments.
     A group precisely similar to the one just described, and of large dimensions, once stood near the village of St. Louis. Its precise location cannot be learned, as it was demolished somewhere between the years 1835-40. This class of mounds will be further noticed under the head of Miscellaneous Works.      

from A. J. Conant's Foot-Prints of Vanished Races in the Mississippi Valley