The correlation of culture sequences provides the basic framework of archaeology, the essential understructure of any interpretations which may follow. In the New World, prehistoric sequence correlations seldom are projected for territories of greater size than the conventional culture area. The southwestern United States, Peru, or, at the largest, eastern North America are classic examples. The reason for such a restriction seems to be that native American cultures but rarely outrun the boundaries of their natural environmental settings, and it is difficult to effect alignments of culture phases or units on an interareal basis.
