Armstrong Tunnel

The Armstrong Tunnels north portal at Forbes Avenue.

The Armstrong Tunnels, opened in 1927, connect Second Avenue, at the South Tenth Street Bridge, to Forbes Avenue between Boyd Street and Chatham Square. The twin-bore four-lane tunnels travel under the Bluff (Boyd's Hill) where Duquesne University is located. The Armstrong Tunnels are noted for the 45-degree curve in the twin horseshoe design and a pedestrian walkway on the western side.

The 45-degree bend and the pedestrian walkway.
The 45-degree bend and the pedestrian walkway.

When Pittsburgh annexed the town of Birmingham (South Side) in 1872, the need arose for better access to the southern shore of the Monongahela River. Most traffic relied on the Smithfield Street Bridge and an old wooden covered bridge at South Tenth Street. Travelers to the Bluff relied on the Fort Pitt Incline, which opened in 1882. When the incline closed in 1906, city steps were built. A metal through truss bridge replaced the wooden structure at Tenth Street in 1904. A proposal to open a passage under Boyd's Hill was seen as a way to relieve traffic in the upper Triangle and increase access to both the northern side of the Bluff and the South Side.

The tunnel portals were designed by City Architect Stanley L. Roush, and Vernon R. Covell of the Allegheny County Public Works Department was the chief engineer. Construction on the 1320 foot bores began in 1926. The Armstrong Tunnels feature Italian Renaissance sandstone walls and cut-stone portals, trimmed with granite. The tunnel vault is concrete. The mysterious 45-degree bend was the result of several factors: mines, geological factors, property rights and alignment with existing roads.

The Armstrong Tunnels north portal at Forbes Avenue.
The Armstrong Tunnels northern portals at Forbes Avenue.

The tunnels were named in honor of Joseph G. Armstrong, Allegheny County Commissioner at the time of construction. Armstrong had previously served as Director of Public Works and Mayor of Pittsburgh. He was very active in much of the infrastructure improvements during the period 1910-1940.

With the increase of traffic brought by the Armstrong Tunnels and the condition of the 1904 truss bridge at the southern portal, a new South Tenth Street Bridge was constructed in 1931. It is Pittsburgh's only conventional suspension river bridge.

The northern portal the Armstrong Tunnels
and the Penn-Lincoln Parkway ramp.
The western portal at the southern end of the Armstrong Tunnels and the Parkway ramp above.

The southern portal of the Armstrong Tunnels, with its stone facing and granite lining, became a familiar site to travelers making their way across the river or along Second Avenue until the construction of the Penn-Lincoln Parkway in the late-1950s. The elevated section of the westbound lanes and the Second Avenue ramp were constructed directly in front of the tunnels, obscuring the portals.

The Armstrong Tunnels north portal at Forbes Avenue.
Approaching the Armstrong Tunnels southern portals from the Tenth Street Bridge.

Renovations were done in the 1980s. The interior walls were partially faced with white ceramic tiles and the sidewalk was protected by a Jersey barrier. The road surface was relaid in concrete. The Armstrong Tunnels were listed as a historic landmark in 1986.

The path of the Armstrong Tunnels under the Bluff.
The path of the Armstrong Tunnels under Boyd's Hill, or the Bluff, and Duquesne University.

Note: Legend states that the 45-degree bend in the tunnel was a mistake and that Chief Engineer Covell committed suicide in shame. This is not true. Vernon Covell lived to build again. As for the curve being a mistake, it's doubtful the engineers could have been off by that much without being aware of it. The general belief is that path was designed to thread its way between and below existing and proposed university buildings. To this day, University architects have been careful in their planning so as not to damage the historic tunnel.

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