The archaeology of Illinois in its present position seems to indicate that the state did not at any time form a distinct single culture or subculture but that it was rather the meeting place of many, due possibly to the rivers that enclose, lead to and intersect its territory. It was at one and the same time a part of one or more widespread patterns or phases and a patchwork of subcultures that extended into neighboring states. There was a tendency for the cultures of the northern four-fifths of the state (roughly north of a line joining East St. Louis with Evansville, Indiana) to be more like the adjacent regions, while those of the remaining counties were more closely related to those of Kentucky, Tennessee, southern Indiana and Missouri and rather readily distinguishable from those of their northern neighbors. There are few instances when it appears probable that a part of the state was invaded by a people of a distinctly differing culture. The Paleo-Indian Big Game Hunters presumably found in Illinois virgin country without previous human occupants. The Baumerians probably entered Illinois from south of the Ohio and expelled or absorbed the conservative Terminal Archaics. Possibly Mortonians intruded into the Black Sand-Red Ocre culture of Illinois from the northwest. Less plausibly, the Stone Vault Grave people may have pushed their way into Adams County from the Gasconade River region of Missouri. The emphasis in this paper has been placed perhaps on the change of cultures. To keep one from getting an erroneous impression of cultural stability, it should be said that, in the writer’s opinion, a culture and subculture contained in greater or smaller areas change gradually through a process of invention here and there and through interchanges of improvements back and forth over a long time. When the change is sufficient to be noted as a “new” culture, the various cultural elements or features are apt to be widely distributed over much the same area. Thus, Baumer seems to have existed for a time alongside Terminal Archaic but finally spread through the southern counties; Hopewellian may have persisted in Calhoun County for a century or more after its collapse to the north and east; and the Final phase may have lingered on in remote portions of the state until Cahokia was past the height of its glory. In general, perhaps it could be said that the southern fifth and the remaining four-fifths of the state were out of step with each other most of the time.