South Mountain and the
Highlands, and here in the Lebanon Valley settled German Moravians,
whose descendants even now retain the peculiar patois known as
"Pennsylvania Dutch." These were late comers to the New World forced to
the frontier to find unclaimed lands. With their followers of both
German and Scotch-Irish origin, they worked their way southward and soon
occupied all of the Virginia Valley and the upper reaches of the Great
Valley tributaries of the Tennessee. By 1755 the obstacle to westward
expansion had been thus reduced by half; outposts of the English
colonists had penetrated the Allegheny and Cumberland plateaus,
threatening French monopoly in the transmontane region, and a conflict
became inevitable. Making common cause against the French to determine
the control of the Ohio valley, the unsuspected strength of the
colonists was revealed, and the successful ending of the French and
Indian War extended England's territory to the Mississippi. To this
strength the geographic isolation enforced by the Appalachian mountains
had been a prime contributor. The confinement of the colonies between an
ocean and a mountain wall led to the fullest occupation of the coastal
border of the continent, which was possible under existing conditions of
agriculture, conducing to a community of purpose, a political and
commercial solidarity, which would not otherwise have been developed. As
early as 1700 it was possible to ride from Portland, Maine, to southern
Virginia, sleeping each night at some considerable village. In contrast
to this complete industrial occupation, the French territory was held by
a small and very scattered population, its extent and openness adding
materially to the difficulties of a disputed tenure. Bearing the brunt
of this contest as they did, the colonies were undergoing preparation
for the subsequent struggle with the home government. Unsupported by
shipping, the American armies fought toward the sea with the mountains
at their back protecting them against Indians leagued with the British.
The few settlements beyond the Great Valley were free for self-defence
because debarred from general participation in the conflict by reason of
their position.

See the separate articles on the states, and also the following
references:--Topographic maps and Geologic Folios of the United States
Geological Survey; Bailey Willis, "The Northern Appalachians," and
C.W. Hayes, "The Southern Appalachians," both