In Colonial times, the Allegheny Mts was where the wilderness began. The mountains we now call the Laurel Highlands – Negro Mountain plus Laurel and Chestnut Ridges – were an enormous impediment to early travel beyond Cumberland, MD, to the Forks of Ohio, now Pittsburgh.
Today, we bike those 140+ miles easily. The GAP, as it has been said, “goes through the mountains, not over them.” This fact is all thanks to eons of time and the fantastic power of erosion.
The Allegheny Mts are ancient. They were formed, then folded into waves of various rocks, like a stack of papers being pushed from either end and then eroded flat. More recently, in geologic time, the region was uplifted, and the roots of the ridges were exposed.
However, rivers meandered across the expanse when the flattened landscape existed. As the land slowly rose, the rivers, powered by gravity, cut into the rising plain and the underlying folds.
With plenty of time, the water cut deep paths into the old mountain roots and formed water gaps. Indigenous people, early explorers, and settlers used water gaps to build practical routes for trails and railroads to cross the Allegheny Mountains barrier.
Today, the GAP, built on a former railroad, follows that same path and plunges through four water gaps.
East to west, the first, at Mile 1.8, is The Narrows. The adjacent hilltops are 1,609′, and the river is 640′, making a gorge 969′ deep. Wills Creek cuts this water gap through the Wills Mountain Anticline. Although it’s not the deepest cut, it’s narrow and feels like a gorge.
The Narrows – Mile 1.8 – 969′ deep.
The second is through Negro Mountain, between Garrett and Rockwood, at Mile 39, the Casselman River cuts through Nego Mt. The adjacent hilltops are around 2435’, and the river is at 1854’. That’s a gorge 581’ deep.
Negro Mountian Water Gap – Mile 39 – 581′ deep.
The most impressive water gap is cut through Laurel Ridge between Confluence and Ohiopyle at Mile 66. The adjacent ridge tops are around 2810’, and the Youghiogheny River is at 1265’. That’s a gorge 1545’ deep—among the deepest in Pennsylvania.
Laurel Ridge Water Gap – Mile 66 – 1545’ deep.
The third water gap is through Chestnut Ridge between Ohiopyle and Connellsville at Mile 82. The adjacent ridge tops are around 2190’, and the Yough at 926’. That’s a gorge 1264 deep.
Chestnut Ridge Water Gap – Mile 82 – 1,264′ deep
All three are water gaps with gently sloping sides, so the feeling of passing through a gorge isn’t readily apparent. Only when you view the rivers from the tops of the surrounding ridges is the vastness of the feature conspicuous.
The best place to get this view is from Baughman Rock, an overlook along Sugar Loaf Road between Ohiopyle and Confluence.
View of the Laurel Ridge Water Gap from Baughman Rock in Ohiopyle State Park
Your next ride on the GAP, through the Allegheny Mountains – aka The Laurel Highlands – stop at these locations and thank gravity and erosion for your ride “Through the mountains, not over them.”