As already remarked, these remains occur mainly in the valleys of the Western rivers and streams. The alluvial terraces, or “river-bottoms,” as they are popularly termed, were the favorite sites of the builders. The principal monuments are found where these “bottoms” are most extended, and where the soil is most fertile and easy of cultivation. At the junction of streams, where the valleys are usually broadest and most favorable for their erection, some of the largest and most singular remains are found. The works at Marietta; at the junction of the Muskingum with the Ohio; at the mouth of Grave Creek; at Portsmouth, the mouth of the Scioto; and at the mouth of the Great Miami, are instances in point. Occasional works are found on the hill tops, overlooking the valleys, or at a little distance from them; but these are manifestly, in most instances, works of defence or last resort, or in some way connected with warlike purposes. And it is worthy of remark, that the sites selected for settlements, towns, and cities, by the invading Europeans, are often those which were the especial favorites of the mound-builders, and the seats of their heaviest population. Marietta, Newark, Portsmouth, Chillicothe, [p007] Circleville, and Cincinnati, in Ohio; Frankfort in Kentucky; and St. Louis in Missouri, may be mentioned in confirmation of this remark. The centres of population are now, where they were at the period when the mysterious race of the mounds flourished.[6]
The aboriginal monuments of the Mississippi valley, the general character of which has been thus briefly and imperfectly indicated, fall within two general divisions, namely, CONSTRUCTIONS OF EARTH OR STONE, comprising «Enclosures, Mounds, etc.»; and MINOR VESTIGES OF ART, including the «Implements, Ornaments, Sculptures, etc.» of the ancient people.
The Earth and Stone Works resolve themselves into two classes, viz: ENCLOSURES, bounded by embankments, circumvallations, or walls; and simple tumuli, or MOUNDS.[7] They constitute, together, a single system of works; but, for reasons which will satisfactorily appear, it is preferred to classify them as above. These grand classes resolve themselves into other subordinate divisions: ENCLOSURES FOR DEFENCE, SACRED AND MISCELLANEOUS ENCLOSURES; MOUNDS OF SACRIFICE, TEMPLE MOUNDS, MOUNDS OF SEPULTURE, etc.