THE first human beings known to have lived in western Pennsylvania were the so-called "Mound Builders," once thought of as a distinct race but now generally believed to have been Indians of the Algonquian stock. What is known of these people is derived from Indian tradition and from archæological examination of their village sites and the mounds they built, for they disappeared from the region before the advent of white men. When they entered the region and when they left or were destroyed are matters of conjecture, but it is certain that their occupation extended over a considerable period of time.
From the evidence of the mounds it appears that the builders dwelt mainly in the great central valley of the continent. Four major areas of occupation have been noted: the upper Mississippi, the lower Mississippi, the Ohio Valley, and the Great Lakes region. Each differed from the others in some characteristics, and even within these areas varying types of cultures are indicated, which may or may not have existed at the same time. Of the mounds themselves four types have been distinguished: the burial mounds, most frequent, consisting of large barrows or tumuli, sometimes conical in shape, heaped over the remains of several persons; the effigy mounds, which represent with surprising fidelity such animal forms as birds, snakes, dogs, and turtles, and were probably of religious significance; the domiciliary mounds, extensive truncated or flat-topped platform mounds on which were built houses and perhaps temples; and the earthwork mounds, including a type obviously built for defense purposes and a type of geometric mound--usually circular or square or a combination of square and circle--which, it is conjectured, was probably social or religious in purpose.
So little scientific investigation of mounds in western Pennsylvania