GEOLOGY: N. M. FENNEMAN 
17 
PHYSIOGRAPHIC SUBDIVISION OF THE UNITED STATES 
By Nevin M. Fenneman 
DEPARTMENT OF GEOLOGY. UNIVERSITY OF CINCINNATI 
Communicated by W. M. Davis, November 24, 1916 
Various attempts at subdivision of the United States into physio- 
graphic provinces have been made, beginning with that of Powell.^ 
The Association of American Geographers, recognizing the fundamental 
importance of this problem, appointed a committee in 1915 to prepare 
a suitable map of physiographic divisions. The committee consists 
of Messrs. M. R. Campbell and F. E. Matthes of the U. S. Geological 
Survey and Professors Eliot Blackwelder, D. W. Johnson, and Nevin 
M. Fenneman (chairman). The map herewith presented and the ac- 
companying table of divisions constitute the report of that committee. 
The same map on a larger scale (120 miles to the inch) will be found in 
Volume VI of the Annals of the Association of American Geographers, 
accompanying a paper by the writer on the Physiographic Divisions 
of the United States. In that paper are given the nature of the bound- 
ary lines and those characteristics of the several units which are believed 
to justify their recognition as such. Though the above-named com- 
mittee is not directly responsible for the statements there made, many 
of them represent the results of the committee's conferences. The 
paper as a whole is beheved to represent fairly well the views of the 
committee, though in form the greater part of it is a revision of a former 
publication. 2 
The basis of division shown on this map, here reproduced, is physio- 
graphic or, as might be said in Europe, morphologic. The divisions are 
based on land forms, not on climate or vegetation. If subdivision were 
carried far enough on the same principle each unit of the lowest order 
would comprise but one physiographic type. In most cases this has 
not been done. Even the units of the lowest order generally embrace 
several types closely associated in their development. 
The genetic classification of land forms is now generally familiar 
to geographers, even to those who do not use it. In this system physi- 
ographic forms are classified according to their histories. Forms which 
result from similar histories are characterized by certain similar features, 
and differences in history result in corresponding differences of form. 
Generally the distinctive features which are important in a genetic 
classification are also obvious to the casual observer, but this is not 
universal. Thus a maturely dissected plateau may grade without a 
break from rugged mountains on the one hand to mildly rolling farm 
