Question: What type of elevation does Allegheny Front and Appalachian Platea have in common?
Context: The Allegheny Front Trail, a relatively new trail in western Centre County, was built collaboratively in the late 1990s by Penn State Outing Club, Ridge & Valley Outings Clubs, Quehanna Area Trails Club, and the Keystone Trails Association.  The trail provides a wide variety of forest environments, including views over valleys to the east, trout streams, and marshlands.  The orange-blazed trail surrounds Black Moshannon State Park and crosses Pennsylvania Route 504 twice, though there is almost no road walking.  Since its inception, the Allegheny Front Trail has changed very little, except for the addition of bog bridges through Black Moshannon Swamp upstream from Shirk Road. The Allegheny Portage Railroad was the first railroad constructed through the Allegheny Mountains in central Pennsylvania, United States; it operated from 1834 to 1854 as the first transportation infrastructure through the gaps of the Allegheny that connected the midwest to the eastern seaboard across the barrier range of the Allegheny Front.  Authorized as part of the Main Line of Public Works legislation in 1824, it was a series of ten inclines connecting to a branch of the Pennsylvania Canal at either end, approximately 36 mi long overall.  It had five inclines on either side of the drainage divide running athwart the ridge line from Blair Gap through along the kinked saddle at the summit into Cresson, Pennsylvania.  The Portage Railroad utilized cleverly designed wheeled barges to ride a narrow-gauge rail track with steam-powered stationary engines lifting the vehicles.  Except for peak moments of severe storms, it was an all-weather, all-seasons operation.  Along with the rest of the Main Works, it cut transport time from Philadelphia to the Ohio River from weeks to just 3–5 days.  The roadbed of the railroad did not incline monotonically upwards, but rose in relatively long, saw-toothed stretches of slightly-sloped flat terrain suitable to animal powered towing, alternating with steep cable railway inclined planes using static steam engine powered windlasses, similar to mechanisms of modern ski lifts. The Pennsylvanian Pottsville Formation is a mapped bedrock unit in Pennsylvania, western Maryland, West Virginia, and Ohio.  The formation is also recognized in Alabama.  It is a major ridge-former in the Ridge-and-Valley Appalachians of the eastern United States.  The Pottsville Formation is conspicuous at many sites along the Allegheny Front, the eastern escarpment of the Allegheny or Appalachian Plateau. The Appalachian Plateau is a series of rugged, high plains located on the western side of the Appalachian Highlands.  The Appalachian Highlands are a mountain range that run down the entire east coast of the United States. Saddle Mountain is a section of New Creek Mountain in the Ridge and Valley physiographic province of the Appalachian Mountains in Mineral County, West Virginia.  The mountain is so named for its shape.  It is best viewed from Skyline which is located to the west along US 50 at the intersection with WV 42, atop the Allegheny Front.  The mountain's elevation is 3074 ft . Blair Gap, one of the gaps of the Allegheny is a water gap along the eastern face atop the Allegheny Ridge or Allegheny Front escarpment.  Like other" 'gaps of the Allegheny' "the slopes of Blair Gap were amenable to foot travel, pack mules, and possibly wagons allowing Amerindians, and then, after about 1778-1780 settlers, to travel west into the relatively depopulated Ohio Country decades before the railroads were born and tied the country together with steel.  Historically, the gap was used for the upper sections of the Allegheny Portage Railroad, which as was authorized by the enabling acts in 1824 of Pennsylvania's Main Line of Public Works as part of the Pennsylvania Canal System which originally envisioned linking Pittsburgh to Philadelphia by canals.  In the early 1900s, US Route 22 followed alongside the watercourse through the gap. The gaps of the Allegheny, 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 ridgelines 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. Kittanning Gap, one of the gaps of the Allegheny, is a now a relatively unimportant wooded ravine (water gap) along the ascent (at the foot) of the Allegheny Ridge "(also called the 'Allegheny Front' or 'Allegheny escarpment')" in central Pennsylvania in the United States.  The gap was one of several optional paths of the Kittanning Path Amerindian trail turned into an emigrant route over the Alleghenies in the day of animal powered technology.  The option up the gap was likely "the 'better choice' of an ascending route" for ox cart and wagon (such as those made downstream in Conestoga, Pennsylvania) encumbered white settlers pouring west across the Alleghenies escarpment. The Kittanning Run is one of the several streams draining the Allegheny Plateau, each one cutting an abrupt valley, one of the gaps of the Allegheny— one of several climbing valleys used for centuries by the Amerindian native peoples to pass East-to-West through the Allegheny Front escarpment, a barrier ridge separating the flat highlands plateau, the Appalachian Plateau—from the many barrier ridges making up the local Ridge-and-Valley Appalachians in the Central Pennsylvania heartland. The Allegheny Front is the major southeast- or east-facing escarpment in the Allegheny Mountains in southern Pennsylvania, western Maryland, and eastern West Virginia, USA.  The Allegheny Front forms the boundary between the Ridge-and-Valley Appalachians to its east and the Appalachian Plateau (locally called the Allegheny Plateau) to its west.  The Front is closely associated with the Appalachian Mountains' Eastern Continental Divide, which in this area divides the waters of the Ohio/Mississippi river system, flowing to the Gulf of Mexico, from rivers flowing into Chesapeake Bay and from there into the Atlantic Ocean.
Answer: mountain