Monadnock (in New Hampshire, nearN.E.Massachusetts), the Blue Hills near Boston, Greylock, in the north-west, and Wachusett in the centre, are the most commanding remnant-summits (known generically as " Monadnocks ") of the original mountain system.
South of the mountains a plateau-like surface - a part of the New England Uplands - broken by residual mountains, or " monadnocks " (a term derived from Mount Monadnock, 3186 ft.
In the north-west, before descent is made to the lowlands of the stratified belt (St Lawrence-Champlain-Hudson valleys, described later on as part of the Great Appalachian valley), and at the same time the rising uplands are diversified with monadnocks of increasing number and height and by mature valleys cut to greater and greater depths; thus the interior of New England is moderately mountainous.
This subdivision is already necessary in Maryland, where the mountain belt is represented by the Blue Ridge, which is rather a narrow upland belt than a ridge proper where the Potomac cuts across it; while the piedmont belt, relieved by occasional monadnocks stretches from the eastern base of the Blue Ridge to the coastal plain, into which it merges.
The uplands are here and there surmounted by residual monadnocks in the form of low domes and knobs; these increase in height and number towards the mountain belt, and decrease towards the coastal plain: Stone Mountain, near Atlanta, Georgia, a dome of granite surmounting the schists of the uplands, is a striking example of this class of forms. The chief rivers flow south-eastward in rather irregular courses through valleys from 200 to 500 ft.