Great Appalachian Valley

The Great Valley, also called the Great Appalachian Valley or Great Valley Region, is one of the major landform features of eastern North America. It is a gigantic trough—a chain of valley lowlands—and the central feature of the Appalachian Mountain system. The trough stretches about 1,200 miles (1,900 km) from Quebec to Alabama and has been an important north-south route of travel since prehistoric times.

Broadly defined, the Great Valley marks the eastern edge of the Ridge and Valley physiographic province. There are many regional names of the Great Valley, such as the Shenandoah Valley. From a large perspective the Great Valley can be divided into a northern section and a southern section.

In its northern section, the Great Valley includes the Champlain Valley around Lake Champlain and the upper Richelieu River that drains it into the Saint Lawrence; the Hudson River Valley, Newburgh Valley, and Wallkill Valley; and the Kittatinny Valley, upper-Delaware River Valley, Lebanon Valley, and Cumberland Valley.

A series of mountains bounds the northern half of the Great Valley on both sides. To the east or coastward side, these include, from north to south, the Green Mountains of Vermont; the Taconic Mountains of Vermont, New York, Massachusetts, and Connecticut; the Reading Prong (which includes the New York–New Jersey Highlands, known variously as the Hudson Highlands, Schunemunk Mountain, and Ramapo Mountains, among other names and sections); and South Mountain in Pennsylvania beyond Harrisburg. There is a wide gap between the Reading Prong and South Mountain at Harrisburg, through which the Susquehanna River passes, connecting the Great Valley with the Piedmont region of southeast Pennsylvania. Some consider this gap the dividing point between the northern and southern sections of the Great Valley.

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