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View southwest (downstream left), Pine Creek beyond trees

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Allegheny County Bridge Number 1 Gourhead Run

Naylor Av over Gourhead Run


USGS 7.5" Topo Quad - UTM Coordinates:
Glenshaw - Zone 17; 0587-4490
Naylor Av

-- Grand Av
-- Bassett La

-- McLaughlin Run

riveted steel plate girder
steel grate deck (on 4 longitudinal beams spaced 4.5 ft on centers)
abutments: locally-quarried sandstone, rock-faced coursed ashlar

27 ft

TOTAL LENGTH (including longest elevated ramp):
55 ft est

6 ft est clearance
16.6 ft wide between girders

1898, Allegheny County
Charles Davis, engineer

During years surrounding 1900, Allegheny County, under the direction of County Engineer Charles Davis, was busy throughout the county building stone arch bridges of a simple and similar design. In some places, however, the crossings were built as riveted plate girder spans. The abutments of these girder bridges exhibit similar stonework to the County's stone bridges -- helping to identify their place in time and origin. A glance at the construction dates indicates that many of the earlier bridge were of the girder type.

One possible explanation for the choice of an arch span versus a girder span may be found in the shape of the land onsite. Where the stream has high banks and can therefore hold rising waters of a flash flood, the bridges are usually stone arches. In places with relatively wide, flat channels, the spans are most often girders. In each instance, the goal was to maintain the level of the road surface as the road approaches and then enters the bridge -- while allowing maximum potential stream flow; sites which made this impractical have since been regraded or replaced.

Other girder bridges akin to this were probably built with open grate deck. Those others have been replaced or altered. McLaughlin's Run Rd in Bridgeville, for example, includes a bridge of this type which has a layer of brick and a layer of asphalt laid over its original open grate.

Allegheny County assigns its bridges with an ID number counting from a stream's outflow, sequentially upstream. This is the first bridge upstream from the point where Gourhead Run flows into Pine Creek (Gourhead Run Number 1).

Older maps (including the 1876 Hopkins map) show the name of this stream as Gourhead Run; more recent maps and records often list the name as "Gourdhead" or"Gourdehead." The Hopkins map shows the name of early settlers in the area having Scotch-Irish surnames: McCaslin, McCully, McClay, McNeal, and others (About 2/3 mile above this bridge, McCaslin's Run flows into Gourhead Run.). Curiosity about the name discrepency led to two possibilities. Named for the Gaelic word for goat, The River Gour flows into Loch Linnhe in the Highlands of Scotland. And the geological term "gour" refers to a formation found in caves and flowing streams. Where mineral-laden streams form small still pools, deposits may build up a raised rim of stone -- the rimstone is a "gour." It is possible, given the course of Gourhead Run through the limestone and other sedimentary rock layers, the early settlers recognized the formations. "Gour" is such an obscure word in either meaning; perhaps later mapmakers transcribed the name into something more recognizable.

Farther upstream on Gourhead Run, northwest of the intersection of Harts Run Rd and Rosanna Dr, the hill rising up is named "Gourhead Knob" on the 1876 map.

The 1876 map also shows Naylor Av as the only road in this area connecting the Allegheny and Butler Plank Road (PA 8) and the Old Butler Turnpike (Mt. Royal Blvd). Duncan Av [Green Belt] was not built until later; Duncan Av crosses Gourhead Run a few hundred feet upstream from Naylor Av on a 1914 county-built concrete arch.

The former importance of the connection at Naylor Rd may be inferred from the site of a toll house on the Butler Plank Rd just south of the intersection of Naylor Av on the right bank of Pine Creek.


field check; cited map; UK Ordnance Survey;

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Introduction -- Nearby Structures

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Last modified: 10-Apr-2003

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