Ancient Aztalan Earthworks


Map of the Aztalan mounds and earthworks
These important works are represented on Plates , and give evidence of greater labor than those at any other locality in the State. They are important also on account of their resemblance or analogy to works in other parts of the United States. It is the only ancient inclosure, properly so called, in Wisconsin; and although it is usually termed a fort or citadel, it will be shown hereafter that it falls more properly into the class denominated “sacred inclosures.” Without this we might be led to suppose that the ancient mound-builders of Wisconsin were a distinct people from those of Ohio, so different is the general character of their monuments. 
The “ancient city of Aztalan” has long been known, and often referred to, as one of the wonders of the western world. Many exaggerated statements respecting the “brick walls” supported by buttresses, the “stone arch,” &c., have been made; for all of which there is little foundation in truth. The remains were discovered in October, 1836, and hastily surveyed in January, 1837, by N. F. flyer, Esq., who soon afterwards published a brief description of them, with a rude wood-cut, in the Milwaukie Advertiser, the first, and then the only newspaper, in this part of the country. This survey was made before there were settlements in the neighborhood, and was done in a cursory manner. The brief account, however, as published, gave a very good general idea of the works; and has been the foundation of all subsequent plans and descriptions up to the present time.

Mr. Taylor’s description1 was furnished by a friend, who only made a brief visit to the works, accompanied by Mr. Hyer, and added but little to our knowledge of these ruins; though it was published in a more permanent and accessible form, and hence is more generally known and referred to. Messrs. Squier and Davis have condensed this description, and copied the plan in their work, in the first volume of the Smithsonian Contributions (page 131, Plate xliv, Fig. 1), with a number of judicious suggestions as to the nature of the walls, the object of the “bastions,” &c. By comparing the plan and description thus given with what follows, the curious reader may trace the differences, and discover wherein the first fell short of presenting the whole truth.
1 Silliman’s Am. Journal, XLIV, 35.

The name Aztalan was given to this place by Mr. Hyer, because, according to Humboldt, the Aztecs, or ancient inhabitants of Mexico, had a tradition that their ancestors came from a country at the north, which they called Aztalan; and the possibility that these may have been remains of their occupancy, suggested the idea of restoring the name. It is made up of two Mexican words, atl, water, and an, near; and the country was probably so named from its proximity to large bodies of water.1 Hence the natural inference that the country about these great lakes was the ancient residence of the Aztecs.2
1 J. Delafield, Jr., Antiquities, &c., p. 107.
2 Buschmann (Ueber d. Aztek. Ortsnamen, p. 6) says the name Aztlan is composed of the lost word aztliand the local termination tlan — Secretary S. I.

Reference to plate will show that the main feature of these remains is the inclosure or ridge of earth (not brick, as has been erroneously stated), extending around three sides of an irregular parallelogram; the west branch of Rock river forming the fourth side on the east. The space thus inclosed is seventeen acres and two thirds. The corners are not rectangular; and the embankment or ridge is not straight. The earth of which the ridge is made was evidently taken from the nearest ground, where there are numerous excavations of very irregular form and depth; precisely such as may be seen along our modern railroad and canal embankments. These excavations are not to be confounded with the hiding-places (caches) of the Indians, being larger and more irregular in outline. Much of the material of the embankment was doubtless taken from the surface without penetrating a sufficient depth to leave a trace at the present time. If we allow for difference of exposure of earth thrown up into a ridge and that lying on the origin 1 fiat surface, we can perceive no difference between the soil composing the ridge and that found along its sides. Both consist of a light yellowish sandy loam.
The ridge forming the inclosure is 631 feet long at the north end, 1,419 feet long on the west side, and 700 feet on the south side; making a total length of wall of 2,750 feet. The ridge or wall is about 22 feet wide, and from one foot to five in height.
The wall of earth is enlarged on the outside, at nearly regular distances, by mounds of the same material. They are called buttresses or bastions; but it is quite clear that they were never designed for either of the purposes indicated by these names. The distance from one to another varies from sixty-one to ninety-five feet, scarcely any two of them being alike. Their mean distance apart is eighty-two feet. They are about forty feet in diameter, and from two to five feet high. On the north wall, and on most of the west wall, they have the same height as the connecting ridge; but on the south wall, and the southern portion of the west wall, they are higher than the ridge, and at a little distance resemble a simple row of mounds.
On the inner side of the wall, opposite many of these mounds, is a slight depression or sinus; possibly the remains of a sloping way by which the wall was ascended from within the inclosure.
The two outworks, near the southwest angle of the great inclosure, are constructed in the same manner; but both these mounds and the connecting ridge are of smaller dimensions. The ridge or way connecting the mounds at a and c, has something of the same general character, though still more obscure. When viewed from the road, a short distance west, these outworks would be supposed to be nothing more than a few circular mounds. The connecting ridge, at least, is too insignificant to be mistaken for the walls of a fort, or other work of defence. Whether these walls are only a series of ordinary mounds, such as are found all over the western country, differing only in being united one to another, it may perhaps be difficult to decide. They may possibly have been designed for the same and for other purposes.
On opening the walls near the top, it is occasionally found that the earth has been burned. Irregular masses of hard reddish clay, full of cavities, bear distinct impressions of straw, or rather wild hay, with which they had been mixed before burning. These places are of no very considerable extent, nor are they more than six inches in depth. Fragments of the same kind are found scattered about; and they have been observed in other localities at a great distance from these ancient ruins.
This is the only foundation for calling these “brick walls.” The “bricks” were never made into any regular form, and it is even doubtful whether the burning did not take place in the wall after it was built. The impression of the grass is sometimes so distinct as to show its minute structure, and also that it was of the angular stems and leaves of the species of carex still growing abundantly along the margin of the river. As indicating the probable origin of this burned clay, it is important to state, that it is usually mixed with pieces of charcoal, partially burned  bones, &c. Fragments of pottery are also found in the same connection. The walls and mounds are composed of a light colored clay, which becomes red on being slightly burned.
From all the facts observed, it is likely that clay was mixed wit the straw, and made into some coarse kind of envelope or covering, for sacrifices about to be consumed. The whole was probably then placed on the wall of earth, mixed with the requisite fuel, and burned. The promiscuous mixture of charcoal, burned clay, charred bones, blackened pottery, &c., can only in this way be satisfactorily accounted for. The pottery was broken before it was buried, for the fragments were scattered about in a manner that clearly shows that the vessels were not entire.
A shaft was sunk by us in the sixth mound from the northwest angle on the west wall. A fragment of galena (sulphuret of lead), and another of iron ore used as red paint, and worn smooth, perhaps by long use in adorning the faces of the red men, were near the surface, and were the only articles found. No burned clay was on this mound, and we soon discovered that it is only in a few places that this substance exists. The earth was here a yellowish sandy loam, entirely free from spots of black mould; thus showing that it was built exclusively from the subsoil of the adjacent grounds. The builders had carefully removed the black soil before they commenced the erection of this mound. Our shaft was sunk some distance below the original surface. Two of the smaller mounds in the interior were also opened, but without results of any interest.

The mound, or projection, or buttress (whichever it may be termed), at the northwest angle of the inclosure, proved to be one of some interest. (See Fig. 14.) After removing the sods with which it was covered, we came upon fragments of pottery, charcoal, half-burned human bones, and numerous amorphous masses of burned clay scattered loosely and promiscuously about in the earthy materials of the mound. This continued to the depth of one foot only; below, the earth was quite uniform in appearance, though still showing incontestable proofs of art. Occasional fragments of clay, charcoal, and fresh-water shells almost entirely decayed, were observed as we proceeded. Still deeper we found a cavity which was nearly filled with loose earth, in which were indications of bones very much decayed and charcoal. This was divided below into two other cylindrical cavities, extending beneath the original surface of the ground, and filled with the same loose materials.
Two bodies had doubtless been buried here in the sitting posture, near each other, enveloped and covered, perhaps, by some perishable substances, which had decayed and left the cavity above; and this shows that the mounds at Aztalan, though constituting an inclosure, were used for burial purposes, as were other ordinary circular mounds. 
Within this inclosure the ground descends towards the river more abruptly near the western wall, forming a kind of second bank, and then with a smooth even surface. This slope is interrupted only by a natural swell or eminence, shown at c, The highest point in the interior is at the southwest corner, and is occupied by a square truncated mound, that, when seen from the high ground at c, presents the appearance of a pyramid, rising by successive steps like the gigantic structures of Mexico.This was doubtless the most sacred spot, as well as the highest. It will be observed that the inclosing walls curve around this pyramid, as if constructed afterwards, and made to conform to the shape of the ground. It is also further guarded by the two outer walls before described.
The level area on the top was fifty-three feet wide on the west side, where, in consequence of the slope of the ground, it has the least elevation; and it was originally, in all probability, a square of this size. On other parts of the mound the sides are high and steep; and the abrading effects of time have acted most upon the summits. There appears to have been a sloping way leading from the top of this mound towards the east; but if so, it has now dwindled to a slight elevation or swell on that side. This road-way was connected with a ridge before alluded to, extending towards the prominent point c. From this last point there is a gradual and easy descent to the river. These level-topped mounds may have been the foundation only of some structure of more perishable materials. From the summit of the two high places, and especially from that at a, the whole works, and quite an extent of surrounding country, can be seen.
At the northwest angle of the inclosure (b) is another rectangular, truncated, pyramidal elevation, of sixty by sixty-five feet level area on the top, with remains of its graded way, or sloping ascent, at the southeast corner, leading also towards a ridge that extends in the direction of the river. This mound occupies the summit of the ridge or bank before spoken of:, though it rises but little, if any, above the top of the adjacent walls. It has been partially destroyed by persons curious in antiquarian research, and by one who, it is said, had been supernaturally convinced that a large amount of money was deposited in it!
There is another square structure (at d), which is level on the top; but as it stands on sloping ground, and has but little elevation, it runs to a grade even with the surface on the upper side. Just at this point a small mound has been erected, perhaps at a subsequent time, and by a different tribe or nation of people.
The analogy between these elevations and the “temple-mounds” of Ohio and the Southern States, will at once strike the reader who has seen the plans and descriptions. They have the same square or regular form, sloping or graded ascent, the terraced or step-like structure, and the same position in the interior of the inclosure. This kind of formation is known to increase in numbers and importance as we proceed to the south and southwest, until they are represented by the great structures of the same general character on the plains of Mexico.
In this inclosure are ridges usually about two feet high, as represented on the plan. The rings or circles connected with them constitute a very peculiar feature, and are supposed to be the remains of mud houses; the materials of the walls having fallen, leaving only a circular mound of earth to mark their original site.1 No ridge exists along the river bank, as represented on Mr. Hyer’s plan; the steepness of the bank probably rendering artificial works unnecessary for the purposes of the builders. Some of the interior ridges, it will be observed, are enlarged at intervals; thus showing an analogy with the main walls and outworks.
1 We are told by Catlin that “the village of the Mandans has a most novel appearance to the eye of a stranger; their lodges are closely grouped together, leaving just room enough for walking and riding between them, and appear from without to be built entirely of dirt. They all have a circular form, and are from forty to sixty feet in diameter. Their foundations are prepared by digging some two feet in the ground, and forming the floor of earth by levelling the requisite space for the lodge. The superstructure is then produced by arranging inside of this circular excavation, firmly fixed in the ground and resting against the bank, a barrier, or wall of timbers, about six feet high, placed on end, and resting against each other, and supported by a formidable embankment of earth raised against them outside. Resting on the tops of these timbers are others of equal size, rising, at an angle of 45°, to the apex or sky-light, which is about three or four feet in diameter, answering also as a chimney. On the top of or over these poles or timbers, is placed a complete mat of willow boughs, of half a foot or more in thickness, that protects the timbers from the dampness of the earth with which the lodge is covered from bottom to top, to the depth of two or three feet, having above all a hard or tough clay which is impervious to water.” — N. Am. Indians, I, 81.

There are two excavations (e and f), the first triangular, and the last circular, which, from their greater depth and regular shape, as well as distance from the walls, were probably not made in the process of obtaining materials for the structures. The excavation at e is so deep, and the soil so tenacious, that water stands in the bottom much of the time, affording a place for the growth of flags1 and other aquatic plants. Perhaps the bottom may have been rendered water-tight by artificial means. Undoubtedly it was once much deeper than at present; the tendency of rains and the accumulation of vegetable matter being to fill it up. The circular excavation (at f) is surrounded by a ridge consisting, doubtless, of the materials thrown out in the digging.
1 Iris versicolor.

Near this point are some springs in a small ravine cut into the bank by the passage of water to the river. This ravine serves also as the outlet of the surface water from within this part of the inclosure. A few stones left along the sides and bottom of this ravine (the force of the water not being sufficient to remove them with the lighter particles of the earth), is all the evidence that could be found of an ancient sewer “arched with stone.” It is quite clear that no such arch existed; nor is there any indication that the aboriginal inhabitants of the American continent were acquainted with the nature of the arch.1 If they were, they certainly did not apply such knowledge in the construction of any works at Aztalan.
1 Even in Yucatan and Central America, where the aboriginal buildings display the greatest advance in architecture, the arch was not used; its substitute being stones laid horizontally, and made to overlap, as represented in Fig. 15 — Stephens’s Yucatan, I, 429.

Nearly the whole interior of the inclosure appears to have been either excavated or thrown up into mounds and ridges; the pits and irregular excavations being quite numerous over much of the space not occupied by mounds. This want of regularity is opposed to the opinion that these excavations were for the cellars of buildings, as suggested by some.
In a letter from Mr. J. C. Brayton, of Aztalan, he says: “Several feet below the surface of the large square mound near the northwest corner of the inclosure was found, a number of years ago, what appeared to be the remains of cloth, apparently enveloping a portion of a human skeleton. Its texture was open, like the coarsest linen fabric; but the threads were so entirely rotten, as to make it quite uncertain of what material they were made.1
1 This is probably the same that was forwarded by Dr. King to the National Institute of Washington. — See Silliman’s Journal, XLIV, 38.

“Numerous fragments of earthenware have been taken from the mounds at different times: portions of broken vessels, varying in size (judging by the curve of the fragments), from a few inches to three feet across the rim.
“A number of rusty gun-locks, in scattered fragments, have been discovered at or near the surface of the ground; and pieces of iron, copper, and brass, have been found in the neighborhood. But all these, being relics of the recent Indian population, fail to throw any light upon the great questions of who made these works, and for what purpose were they constructed. The Winnebagos, the last occupants of this interesting locality, always answer in the negative by a significant shake of the head, when asked if they can tell who erected the mounds.”
Mr. Brayton, who has resided in the vicinity of these works since their discovery, is of the opinion that none of the mounds have sensibly changed from natural causes since the first settlement of the country in 1836.
Our examination of the tumuli exterior to the inclosure led to no very important results. The third from the north end of the long row, seen on the plate (about four feet high and thirty feet in diameter), was penetrated to the bottom, and the opening enlarged below in every direction. A post (apparently tamarack) had been inserted, and was now all decayed, except a portion near the bottom.1 This may have been set in since the building of the mound, which was composed of black and yellow soil intermixed, having beneath gravel composed mostly of limestone pebbles. If these smaller tumuli ever covered any deposits, they are now so completely decayed that not the least trace of them can be discovered.
1 This post may have been the remains of a medicine pole, such as was erected by the Mandans. According to Mr. Catlin, the Mandans were in the habit of erecting mounds of earth near their villages about three feet high, around which were arranged in circles the skulls of the dead, after their bodies had decayed on the scaffolds. On each mound was erected a pole, hung with articles of mysterious and superstitious import. Something of this kind may be the origin of the numerous smaller mounds in Wisconsin, in which no traces of artificial or human deposits could be found—See N. Am. Indians, I, 190.

While at Aztalan we were informed that upon opening one of the larger mounds some years ago, the remains of a skeleton were found, inclosed by a rude stone [page 48:] wall, plastered with clay, and covered with a sort of inverted vase of the same materials.
A number of these mounds have been opened at different times, and their contents, having been carried away to various parts of the world, cannot now be recovered.
With the view of ascertaining the contents of the larger elevations for ourselves, we selected one in Mound Street, ten feet in height, and sixty feet in diameter at the base, into which a trench four feet wide was dug, extending from the south side to beyond the centre, and down to the subsoil or stratum of gravel that underlies the superficial covering of vegetable mould.
The earth was quite uniform throughout; consisting of dark-colored mould and yellowish sandy loam, mixed in small quantities. Ashes, mingled with charcoal, were observed as we went down, and occasionally fragments of human bones. No skeleton was found; no stonework or earthenware — no stone or metallic implements of any kind could be discovered. Bones of some burrowing animals, and the remains of a fish were taken out. Fragments of rotten wood, apparently oak, were found at all depths. They were not charred, nor did they appear to have had any definite arrangement, but were confusedly placed, as if carelessly thrown upon the mound during the progress of its construction.
From the oft-repeated indications of fire at various depths, we could draw no other conclusion than that this was a “mound of sacrifice” and that at each repetition of the ceremony an addition was made to the height of the mound.
The gopher1 often burrows in the artificial tumuli to find a dry place for its nest; and roots of trees penetrate to their lowest depths.
1 The name here universally applied to the thirteen-lined marmot (Spermophilus tridecemlineatus).

The question naturally arises in the mind of the observer, For what purpose was this great inclosure made? Mr. Hyer called it a citadel, and it is usually termed “the fort,” and supposed to be a work of defence — a place to which the mound-builders resorted for safety when hard pressed by an enemy. Various reasons have been assigned for this supposition. Its connection with the river, affording a means of supply to the besieged — its buttresses or bastions — its outworks — its watch-towers — might all seem to convey the idea of a military work or a fortification.
Although when we attempt to describe these remains, the technical terms of military men are found convenient, and sometimes applicable; yet the “fort,” the “buttresses,” the “bastions,” &c., have but remote resemblance to such constructions. Expressions like these often lead the superficial observer and reader astray, and may have done so in this case.
Messrs. Squier and Davis show very conclusively that the circular projections on the exterior of the walls could not have been intended for bastions.1 It is equally clear that a ridge of earth twenty-two feet wide and five feet high, does not need the support of buttresses.
1 Smithsonian Contributions, I, 132.

But this fort is entirely commanded from the summit of a ridge extending along the west side, nearly parallel with and much higher than the west walls themselves, and within a fair arrow-shot; so that an enemy posted on it would have a decided advantage over those within the defences. This ridge would also constitute an excellent breastwork to protect an enemy from the arrows or other weapons shot from the supposed fort. As if purposely to assist an approaching enemy, a number of mounds have been erected along the ridge, affording secure hiding-places and look-out stations, very convenient to the attacking party. These may, however, have been erected at a more recent date.
Again, the large mounds of the remarkable row northwest of the inclosure are not in connection with it, but are excellent points from which to reconnoitre and annoy the occupants of the supposed fortress.
From the summit of the ridge before alluded to, as will be seen by the sections on Plate XXXV, the ground descends towards the river; so that the inclosure is on a declivity, and is thus commanded from the opposite side of the river. Here, again, as if purposely to render aid and comfort to an enemy, a breastwork is erected, extending along the margin of the stream, from behind which arrows or other weapons could be thrown directly into the fort by persons lying in perfect security.
From the skill exhibited by the mound-builders in their works of defence in other portions of the West, we cannot imagine that they would construct such a fort as this; we might at least expect that the walls would be extended so as to include the ridge parallel to it. There is no guarded opening, or gateway, into the inclosure. It can only be entered by water, or by climbing over the walls.
The only ancient work resembling this in its general features heretofore described, is that of Tuloom, in Yucatan, of which an account is given by Mr. Stephens, and quoted by Mr. Squier.1 This is an inclosure of about the same dimensions, and bounded on the east by the sea; it consists of a loose stone wall, with watch-towers at the two west corners, corresponding with the two large pyramidal mounds at Aztalan, except that they are placed on the walls.
1 Yucatan, II, 396; Aboriginal Monuments of New York, p. 98, in Smithsonian Contributions, Vol. II. In the accompanying figure the arrow, indicating the cardinal points, is reversed.

Mr. Stephens represents his as a walled city; but it must be admitted that only a very small city can be included in a space fifteen hundred by six hundred and fifty feet, or twenty-two and a half acres. Mr. Squier thinks that this structure was erected for some sacred object, though used, probably, as a place of defence in a last resort; and, in view of all the facts before stated, it may be inferred that the inclosure at Aztalan was intended for similar purposes, and not primarily occupied as a place of defence.
We may suppose it to have been a place of worship; the pyramidal mounds being the places of sacrifice, like the teocalli of Mexico. From its isolated situation — there being no other similar structure for a great distance in any direction — we may conjecture that this was a kind of Mecca, to which a periodical pilgrimage was  prescribed by their religion. Here may have been the great annual feasts and sacrifices of a whole nation. Thousands of persons from remote locations may have engaged in midnight ceremonies conducted by the priests. The temple, lighted by fires kindled on the great pyramids and at every projection on the walls, on such occasions would have presented an imposing spectacle, well calculated to impress the minds of the people with awe and solemnity. That these works were designed for some such uses, seems quite probable.
 represents the same structures on a smaller scale, and shows their relation to the neighboring country. It will be seen that, excepting a few mounds, no other artificial works are connected with the great inclosure; nor do these present that variety of imitative forms so common in other localities. Half a mile off, in a southwesterly direction, is a square pyramidal mound, similar to those within the inclosure.
Do not these facts warrant the suggestion that the people of Aztalan, in Wisconsin, were a different people, in many respects, from those who erected the animal-shaped mounds? This location may possibly have been occupied by a colony of Mexicans; since we know that colonies were sometimes sent out by that singular people.1