Gaps of the Allegheny

The barrier ridge of the Appalachian Mountain chain extends from New England to Georgia, and Alabama. Some of the local names, such as the Alleghenies for parts of the chain are marked; others are labeled on other maps on this page. Through the Appalachians west of the Berkshires, there were just five openings allowing east to west animal-powered travel within the United States up until the 1930s,[a] giving emphasis as to the importance of the three interiors mountain passes like the Gaps of the Allegheny Ridge.
Location of Kittanning Gap after GNIS finding of 'Kittanning Gap, Pennsylvania' seen in USGS National Map viewer screenshot. The gap is located effectively in a western suburb of Altoona.
 • The maps on this page also are showing the nearby PRR Horseshoe Curve which crosses watercourses cutting three other gaps. GNIS software shows the Gap with the indicated 'A' marker well below the mouth of Kittanning Run.
 • The Kittanning Gap name likely signifies a 'choice way' of climbing the escarpment to wagons or mule trains on the way to the west side of the Allegheny Mountains and Kittanning, PA. Taking a right through the gap to climb up the escarpment was a bit easier than either steep narrow creek beds straight ahead. This was one alternative routing through the area along what the 19th century would call the Kittanning Path.
This 1827 map shows the political map, the main water courses, and their relation to the key barrier ridges as seen by a reputed cartographer preparing this official map in the early years of the Main Line of Public Works (1824). The Allegheny Ridge is prominently shown in the map center-left, the gaps of the Allegheny Front are located in the border area between Cambria County (uplands) and Huntingdon County (lowlands).
USGS - Appalachians Mountain chain showing the lines of the barrier ridges in central, western, and northwestern Pennsylvania. Counting the Hudson Valley north of the Catskills in New York and the southern end of the chain on the Georgian plains, there are exactly three narrow areas where water gaps allowed climbing up to mountain passes allowing passage across the mountains was possible to animal pulled transport vehicles.
USGS combined topological and relief map mode view with search object "Kittanning Run". The Web software identifies the search item with short yellow point icon containing the 'A' (circled). This "official USGS confluence" is several miles from the official USGS Kittanning Gap; the dark trace forming a hairpin turn directly below the marker is the Pennsylvania Railroad's famous Horseshoe Curve.
A closer look at the Appalachians and regional subordinate mountain ranges across New York State and New England.
USGS - Appalachians Mountain chain geomorphological classification zones in the Eastern United States.

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.

This profile of the Allegheny Portage Railroad crossing the Allegheny Front gives valuable perspective at how the escarpment of the front and steepness of the gaps of the Allegheny created the final barrier range preventing easy settlement of the colonial and post-revolutionary-war west (today's Mid-west). It also illustrates the upland nature of the western side of the Front, the Allegheny Plateau but less clearly demonstrates the general barrier range nature of the other ridgelines of the Ridge-and-Valley Appalachians.


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  1. ^ Josephy, Jr., Alvin M., ed. (1961). The American Heritage Book of Indians. American Heritage Publishing Co., Inc. pp. 188–219. LCCN 61-14871. [About the collapse of the Susquehannocks nation]: In that decade, Pennsylvania, Connecticut, and New York all claimed the Susquehannock lands of the Wyoming Valley, where the remnants of the nation were to recoil into a few scant under populated towns. In 1678, the Governor of New York would sign a treaty with the League of the Iroquois requiring them to take in the Susquehannocks. The Iroquoian cultures universally supporting adoption, absorbed the people. Small bands moved west across the Susquehanna to new villages such as Conestoga Town and some are believed to have trekked through the gaps of the Allegheny [emphasis added] to the virtually empty lands beyond the Alleghenies, perhaps mingling there with other Iroquoian peoples such as the Seneca, Wenro and Erie peoples forming the new clans and towns as the (new) Mingo people whose small bands known to be present in Western Pennsylvania and Eastern Ohio in the early 1800s.
  2. ^ J. Simpson Africa (1883). Louis H. Everts (ed.). "History of Huntingdon and Blair Counties, Pennsylvania". Philadelphia: J.B. Lippincott & Co. p. 24. On the 30th of the same month, Maj. Robert Cluggage, in writing to Col. Piper from Huntingdon, reports that lurking bands of Indians had been at one of the gaps of the Allegheny, and that ... [Emphasis added]