Tribal distributions depicted on these maps (and on all other tribal maps covering a comparable area) are arbitrary at many points. Detailed knowledge of tribal areas was acquired at different times in different regions. For example, by the time knowledge was gained of the areas occupied by Plains tribes, many groups in the East had become extinct or had moved from their aboriginal locations. Some of these movements ultimately affected distributions on the Plains prior to reasonably detailed knowledge of Plains occupancy. Hence, it is not possible to approximate aboriginal areas of occupancy on a single map of continental scope. Furthermore, most groups did not occupy sharply defined areas, so that the delineation of territories is misleading.
Distributions were derived, with slight modifications, from Indian tribes of North America (Driver and others, 1953), and boundaries within California were simplified after Languages, territories, and names of California Indian tribes (Heizer, 1966). According to the authors of these publications, the boundaries shown are those of the mid-17th century in the Southeast and the eastern part of the Northeast, the late 17th and early 18th centuries farther west in the Northeast, the late 18th and early 19th centuries in the Plains, the late 18th century in California, and the middle-to-late 19th century elsewhere. Even so, many compromises had to be made.
Culture areas, which indicate groupings of tribes of similar cultural type, are after "Comparative studies of North American Indians" (Driver and Massey, 1957), with revisions by William C. Sturtevant in consultation with John C. Ewers, Smithsonian Institution. Boundaries are arbitrary in many places because the basis of classification is vague and distributions of most cultural traits do not coincide. The groupings shown are fairly representative of classifications found useful by several generations of anthropologists.
Genetic relationships between Indian languages are shown on these maps. Subgroupings of more closely related languages and several remote relationships are omitted. The linguistic stocks are based on "Languages of the world: Native America fascicle one" and "Languages of the world: Native America fascicle two" (Voegelin and Voegelin, 1964 and 1965), and Map of North American Indian languages (Voegelin and Voegelin, 1966). A few modifications and corrections were made by the present author (partly following suggestions by Ives Goddard, Harvard University, and Dell Hymes, University of Pennsylvania).
Research on this subject is advancing rapidly. These maps try to give a reasonable balance between fact, probable fact, and probable future opinion and take into account some of the unevenness of data and of research in different regions and different stocks.
Driver, Harold E., and Massey, William C., "Comparative studies of North American Indians," Am. Philos. Soc. Trans., new ser., v. 47, pt. 2, 1957, p. 172-174
Driver, Harold E., and others, Indian tribes of North America, Mem. 9, Internat. Jour. of Am. Ling., Baltimore, Waverly Press, 1953
Heizer, Robert F., Languages, territories and names of California Indian tribes, Berkeley and Los Angeles, Univ. of California Press, 1966
Voegelin, C. F., and Voegelin. F. M., "Languages of the world: Native America fascicle one." Anthropo. Ling., v. 6, no. 6, 1964