Northern Turnpike & Thompson Run, Allegheny County, PA
One of the best hidden treasures of local civil engineering lies on one of the abandoned bits of Northern Pike (an original section of a major Pgh-Phil highway since replaced by various alignments of Old Wm Penn Hwy, New Wm Penn Hwy [current Bus US 22], and the Parkway East Extension I-376).
Visiting the Northern Pike crossing of Thompson Run at Halls Station requires a bit of a hike. From the intersection of Old Wm Penn and Jefferson Heights Rd in Penn Hills, drive south to cross the bridge over the Parkway. Turn left (east) on Nike Drive [named after the location of one of the Defense Dept now decommissioned missile installations?]. Nike Drive splits off to the left while Northern Pike continues down the hill. This area is a 1950s subdivision. In less
than a mile, the suburban road ends as it becomes a private driveway. Park in the "wide" area to the right. The original path of Northern Pike continues down through the woods...no asphalt or other hard road surface remains, if it were ever there, which I doubt. Hike down the hill; I'd estimate it to be a little more than a mile. At the bottom, you'll reach Thompson Run.
The bridge there is probably from the late 1800's, between 1870 and 1900. Most other similar bridges in Allegheny County have been rebuilt and altered severely. This one still has the original (rotted) wooden deck. [Span now partially collapsed.]
Following the Union RR tracks north, an iron bridge carries Thompson Run Rd over the tracks. It's closed and blocked from traffic by piles of dirt and barricades. The surface is asphalt now, but you can see telltale cracks indicating the old surface structure.
Further up the valley there is a pair of concrete bridges which at first look like twins joined at a 90 degree angle. They were built a few years apart...around 1910...the dates are on the bridges. One carries Old Wm Penn Hwy over Thompson Run. The other carries Thompson Run Rd over Leak Run.
The next bridge north which crosses Thompson Run, carrying Frey Rd, is a severely altered twin of the Northern Pike bridge. It once had a wooden deck and more decorative railings...but all of that is gone.
Back the other way, south of the Northern Pike bridge, there is a newly redecked bridge which carries Thompson Run Rd over the creek of the same name...just before the road passes through a concrete tunnel under the Union RR. this bridge had a wooden deck, but they just finished a new steel and concrete deck. The railings have been replaced by standard issue guardrail. The piers and abutments are original and surprisingly decorative in a utilitarian way...cut stone.
Farther down Thompson Run Rd at the intersection with Lower Rodi Rd, there is another concrete tunnel running under the RR. If you walk along the creek through the tunnel you will come to the remains of one more abandoned bridge with a wooden deck. Barely passable even on foot, this bridge leads to an old abandoned road which angles up the side of the hill to the Queen Farm (Queen Dump). Cool old wooden guardrail along there. Foundations of old houses and springs. An older map names the road Buena Vista, but it's not passable except on foot or bike, and the area farther up the hill is posted No Trespassing.
Following Larimer Ave further south from this location, there is one of the few open steel grate bridges around here at Railroad St crossing Thmopson Run. It's a somewhat intricate truss.
Most of this will probably be gone when they build the new highway
through this valley.
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