Gaps of the Allegheny

The gaps of the Allegheny,^[1][2] meaning gaps in the Allegheny Ridge (now given the technical name Allegheny Front) in west-central Pennsylvania, is a series of escarpment eroding water gaps (notches or small valleys) along the saddle between two higher barrier ridge-lines in the eastern face atop the Allegheny Ridge or Allegheny Front escarpment. The front extends south through Western Maryland and forms much of the border between Virginia and West Virginia, in part explaining the difference in cultures between those two post-Civil War states. While not totally impenetrable to daring and energetic travelers on foot, passing the front outside of the water gaps with even sure footed mules was nearly impossible without navigating terrain where climbing was necessary on slopes even burros would find extremely difficult.

The gaps, formed by small streams, provide several usable incline planes, or ramps, connecting the eastern river valley lowlands to the highlands atop the plateau to the west and north, that would otherwise have been unnavigable by animal powered wagons before the mid-1930s. As the map at right indicates, there were but five ways west from the eastern seaboard (colonies) to beyond the Appalachians barrier ridges. The gaps in the Allegheny, all west of present-day Hollidaysburg and Altoona, are by Hurlbert grouped as part of the Kittanning Gorge, with the eponymous name borrowed from the Lenape (Delaware nation, once centered in the Delaware Valley, ranging from New York Harbor to the northern Chesapeake, occupying the Lehigh Valley and eastern Pennsylvania, New Jersey, and Delaware), but made immigrants forced west of the Mountains into empty lands during the 18th century.

The streams cutting those various gaps either let out into the Susquehanna River tributaries, the Juniata River, or the West Branch of the Susquehanna, so gave the rich Pennsylvania Dutch country access to the interior and the ramp-like valleys climbing to the divide, as did the Main Branch of the Susquehanna and its tributaries climbing to the ridges overlooking both the Hudson and the Mohawk Valleys.

Hurlbert, in his study The Paths of Inland Commerce, makes a distinction between the gaps leading up from the Susquehanna across the divide from the Allegheny River, those in between the Monongahela and the Allegheny, and those reachable across the divide between the Potomac River, and the Monongahela and the Cheat Rivers — only grouping the first batch in his usage of gaps of the Allegheny.

Traversing the line of the Alleghenies southward, the eye notes first the break in the wall at the Delaware Water Gap, and then that long arm of the Susquehanna, the Juniata, reaching out through dark Kittanning Gorge to its silver playmate, the dancing Conemaugh. Here amid its leafy aisles ran the brown and red Kittanning Trail, the main route of the Pennsylvania traders from the rich region of York, Lancaster, and Chambersburg. On this general alignment the Broadway Limited flies today toward Pittsburgh and Chicago.

A little to the south another important pathway from the same region [i.e. Susquehanna basin] led, by way of Carlisle, Bedford, and Ligonier, to the Ohio. The "Highland Trail" the Indian traders called it, for it kept well on the watershed dividing the Allegheny tributaries on the north from those of the Monongahela on the south.

Farther to the south the scene shows a change, for the Atlantic plain widens considerably. The Potomac River, the James, the Pedee, and the Savannah flow through valleys much longer than those of the northern rivers. Here in the South commerce was carried on mainly by shallop and pinnace. The trails of the Indian skirted the rivers and offered for trader and explorer passageway to the West, especially to the towns of the Cherokees in the southern Alleghanies or Unakas; but the waterways and the roads over which the hogsheads of tobacco were rolled (hence called "rolling roads") sufficed for the needs of the thin fringes of population settled along the rivers.

Trails from Winchester in Virginia and Frederick in Maryland focused on Cumberland at the head of the Potomac. Beyond, to the west, the fingertips of the Potomac interlocked closely with the Monongahela and Youghiogheny, and through this network of mountain and river valley, by the "Shades of Death" and Great Meadows, coiled Nemacolin's Path to the Ohio. Even today this ancient route is in part followed by the Baltimore and Ohio and the Western Maryland Railway.

The terms gaps of the Allegheny and the formal geology term, the Allegheny Front, are from two different disciplines. The former is used by historians (most often) describing the local measures taken during the French and Indian War and Native American territories before the United States Constitution, or discussing the transport network east to west before the 1930s depression's public works projects drove hundreds of roads into and through the mountains years after wagon road turnpikes established corporate through-ways that generally went out of business with the rise of railroads.

These low water gaps of the Allegheny are located in an arc in the depression between higher barrier ridge-lines, a family or succession of half-mountain passes letting out in a similar series of water courses, albeit rising more gradually from the west, where the depressed upland was caused by the weight of the immense plateau glacier that flattened the Appalachian Plateau long ago. In the days before academia formed committees to standardize terms, place names were generally applied locally, copied by the USGS making regional maps, and in that era the last escarpment rising to the Allegheny Plateau was generally known as Allegheny Mountain or the Allegheny Ridge or just The Allegheny. The modern term of art, the Allegheny Front, was coined by physical geologists and other earth scientists interested in geomorphology reasoning out the processes that make one landscape terrain different from another in time, cause and space.

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