De Soto traversed the Chatta-Muskogee region, when, in 1540, he discovered the Mississippi. He found there a numerous population lodged in well-constructed dwellings, and with their council-houses surmounting lofty mounds. De Soto and later travellers noted their extensive fields of maize, beans, squashes, and tobacco, and their well-finished flint implements. They were Mound-Builders; and though no longer manifesting in extended geometrical earthworks the special characteristic of the old race, it is assumed that in them we recover traces of the vanished people of the Ohio valley.
With this assignment of the Mound-Builders to an affinity with Indian nations still represented by existing tribes, the vague idea of some strange prehistoric American race of remote antiquity vanishes; and the latter tendency has been rather to underestimate their distinctive peculiarities. Some of these seem to separate them from any Indian tribe of which definite accounts have been preserved; and foremost among them is the evidence of comprehensive design, and of scientific skill in the construction of their sacred enclosures. The predominant impression suggested by the great military earthworks of the Mound-Builders is that of a people co-operating under the guidance of approved leaders, with a view to the defence of large communities. Elaborate fortifications are erected on well-chosen hills or bluffs, and strengthened by ditches, mounds, and complicated approaches; but the lines of earthwork are everywhere adapted to the natural features of the site. The sacred enclosures are, on the contrary, constructed on the level river-terraces with elaborate artificiality of design, but on a scale of magnitude not less imposing than that of the largest hill-forts. On first entering the great circle at Newark, and looking across its broad trench at the lofty embankment overshadowed with tall forest trees, my thoughts reverted to the Antonine vallum, which by like evidence still records the presence of the Roman masters of the world in North Britain 1700 years ago. But after driving over a circuit of several miles, embracing the remarkable earthworks of which that is only a single feature, and satisfying myself by personal observation of the existence of parallel avenues which have been traced for nearly two miles and of the grand oval, circles, and octagon, the smallest of which measures upwards of half a mile in circumference, all idea of mere combined labour is lost in the higher conviction of manifest skill, and even science. The octagon indeed is not a perfect figure. Its angles are not coincident, but the sides are very nearly equal; and the enclosure approaches so closely to an accurate figure that its error is only demonstrated by actual survey. Connected with it by parallel embankments 350 feet long, is a true circle, measuring 2880 feet in circumference; and distant nearly a mile from this, but connected with it by an elaborate series of earthworks, is the great circular structure previously referred to. Its actual form is an ellipse; the different diameters of which are 1250 feet and 1150 feet respectively; and it encloses an area of upwards of 30 acres. At the entrance the enclosing embankment curves outward on either side for a distance of 100 feet, leaving a level way between the ditches, 80 feet wide, and at this point it measures about 30 feet from the bottom of the ditch to the summit. The area of the enclosure is almost perfectly level, so that during rain-floods the water stands at a uniform height nearly to the edge of the ditch.