In the upper Ohio Valley, Adena mounds and their burials are less complex than, but essentially similar to, those of the major Adena centers of Ohio and Kentucky. Chronologically, they belong in the middle and late Adena periods. Two Adena sites much farther east have been found on Chesapeake Bay; they are closer in trait inventories and in radiocarbon dates to upper Ohio Valley sites than to Adena sites farther west. A reappraisal of evidence from the Northeast, particularly the Middlesex focus of New York, strongly suggests the movement of Adena people as far as the St. Lawrence River, although the proportion of Adena traits diminishes as distance from the Ohio Valley increases. Still another Adena dispersal, probably contemporaneous with this one, has previously been postulated to account for the Copena complex of Tennessee and Alabama. The cause of these rapid and far-reaching movements was probably the arrival or growth of Hopewell people in Illinois and Indiana and soon after in Ohio.