PHYSIOGRAPHIC EXTENSION OF UNITED STATES — 245 
so nearly obliterated that history must begin with the surface 
changes of the Pleistocene epoch. These were the changes incident 
to the advance and retreat of several ice sheets. The United 
States and Canadian divisions of the section were similarly and 
contemporaneously affected. Post-Pleistocene history is largely 
a record of drainage readjustments following the final disappearance 
of the ice. 
THE NEW ENGLAND PROVINCE 
East of the Hudson-Champlain Valley and south of the St. 
Lawrence River lies the New England region. Physiographers 
regard it as a province in the major division of the Appalachian 
Highlands. It is bounded on the east by the Atlantic Ocean, and 
on the west by a line running north from Long Island Sound along 
the eastern border of the Hudson-Champlain Valley’ to the foot of 
Lake Champlain, thence northeast to the city of Quebec and down 
the St. Lawrence Valley.2, Newfoundland, though detached and 
separated from the mainland by a considerable body of water, is 
really an outlier of this province and will be treated as a section of it. 
Exclusive of the coastal margin, New England topography is 
largely of the type of an uplifted, extensively dissected, and 
glaciated peneplain. To this general characterization, however, 
must be added certain modifications. Although the terms “up- 
land” and “plateau”’ may be properly applied to the southern half, 
a part of the northern half is so mountainous as quite to conceal the 
plateau feature. The Connecticut Valley must also be considered 
as departing from the general characterization. The topography 
is controlled by three prominent structural features, namely: (1) 
a western mountain axis, extending through Connecticut, Massa- 
chusetts, and Vermont; (2) an eastern mountain axis, unimportant 
topographically in the United States, which runs from Rhode Island 
to the Maritime Provinces of Canada; and (3) a long, narrow, 
structural depression between these two axes, in part occupied by 
the Connecticut Valley. 
Each of these mountain axes was early in geologic time a 
line of elevation. The northern part of each still retains the 
tN. M. Fenneman, Ann. Asso. Am. Geog., IV, 101-4. 
2C. A. Young, op. cit., p. 108. 
