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In the latter part of the 19th century, the city of Pittsburgh was growing rapidly to the east, the north, and on the South Side. However, the 5 mile long, 400 foot obstacle called Mount Washington posed a major barrier to development in the South Hills area.

With transportation basically limited to horse-drawn wagons and walking, residents of the South Hills had to rely on a series of inclines to traverse the hill, or take the long way to the city down Saw Mill Run to the West End. These difficulties slowed South Hills development and the area retained a rural flavor as mostly farmland.

In 1904, a streetcar tunnel was built at the South Hills Junction and rail traffic was extended to the South Hills. This and the advent of the automobile accelerated development in the Brookline area and points south, like Dormont and Mount Lebanon. As the population grew, so did the amount of vehicular traffic, and it soon became necessary to find a better way to get traffic to and from the downtown area.

In 1909 residents of the South Hills persuaded the county commissioners that a tunnel would be a boon to the region, and it was agreed that a tunnel through Mount Washington and a bridge over the Monongahela River were essential to the growth of the city, but no plans were in place and no promises were made as to when such a project would begin.

Over the next 10 years, many proposals were put forward for consideration. One actually envisaged no tunnel at all, but rather a deep, 2 mile cut right through the heart of Mount Washington. In 1919, the County Planning Commission awarded a contract to Booth and Flinn, Ltd., and construction of the Liberty Tunnels began.

The boring of the tubes was completed in 1922, and by the beginning of 1924, construction was nearly completed and the new tunnels were opened to traffic. At the time they were considered an engineering marvel. The nearly two-mile span was the longest tunnel in the country at that time.

One unique problem was the issue of the ventilation of automobile exhaust. Soon after the opening of the tunnels there was a mass-transit strike that idled the city's trolley service. People turned to their automobiles, and during rush hour jams, many motorists literally passed out at the wheel due to the dangerous buildup of carbon monoxide gas.

Until a solution could be found, the city began counting vehicles and tunnel use was restricted. Tunnel engineers worked with the U.S Bureau of Mines to design a ventilation system that consisted of two pairs of 200-foot vertical shafts that continuously pumped fresh air into the tunnels from a mechanical plant located atop Mount Washington.

These shafts were completed and operational in 1928, and traffic restrictions were eliminated.

The South Portal of the new tunnels exited onto the intersection of Saw Mill Run and West Liberty Avenue. The North Portal exited onto the newly completed McCardle Roadway. At the exit to the North Portal was a decorative traffic circle containing a monument. Over time this circle became a hindrance to traffic and was reduced in size. Eventually, a traffic signal only was present, and ultimately the obstacle was eliminated.

The new tunnels made a huge difference in travel time from the South Hills to the South Side of Pittsburgh, but getting to the downtown area still required getting down to Carson Street and over the Smithfield Bridge. This congestion was relieved by the construction of the Liberty Bridge.

Construction of the span began in 1925 and was completed in March 1928. Traffic now could exit the tunnels and travel directly over river to ramps that led to the Boulevard of the Allies and Forbes Avenue. A journey that once took hours was now completed in a matter of minutes, and this convenience led directly to a boom in the real estate values of South Hills property, and Brookline grew rapidly as a result.

Over the years the Liberty Tunnels have remained basically the same. In 1939 the road was repaved, and new lighting and drainage were installed. In the mid-1970s the Tubes received their second overhaul, with a new road bed installed, new lighting, and the removal of the long abandoned walkways to enlarge the road surface. Years of dirt and grime were removed from the inside, and the outside facades were reconstructed.

One problem that became evident shortly after the original opening of the Tunnels was the traffic congestion at the intersection of Saw Mill Run and West Liberty Avenues. By 1932 there were 25,000 vehicles using the tunnels each day, already exceeding their designed capacity. By the end of the century that number was up to nearly 80,000.

Since the mid-1930s there were a number of proposals to rebuild the intersection in a way that better facilitated the numerous traffic patterns at the crowded intersection. Not until 1999, with the pending closure of the Fort Pitt Tunnels looming on the near horizon did the city act on the issue. A new intersection/bypass was constructed and what was once a dreaded snarl of rush hour traffic became a simple one or two light delay.

In addition to the new intersection, engineers made some improvements to the tunnels themselves, installing a new cement roadbed, repainting the walls, and installing new reflective barriers on the sides of the roadway. The new roadbed and the ease of travel created by the new intersection were a huge upgrade in convenience for South Hills travelers.

Below are links to some fascinating photos of the Liberty Tunnels, the Liberty Bridge, and the intersections at the north and south ends.

The Old Bell House at Saw Mill Run - 1890
Saw Mill Run Road at West Liberty Avenue - 1915
West Liberty Avenue at Pioneer Avenue - July 1915
West Liberty Avenue at Pioneer Avenue - Oct 1915
Construction of the North Portal - (1919-1924)
Construction of the South Portal - (1919-1924)
Structural Steel Ribbing Line the Tunnels - 1922
Artist's Conception of Liberty Bridge - 1924
Construction of the Liberty Bridge - (1925-1928)
Saw Mill Run Road at West Liberty Avenue - 1925
Liberty Bridge Dedication - March 27, 1928
Saw Mill Run Road at West Liberty Avenue - 1931
The Liberty Bridge in Full Color - 1939
To the Bungalow Life in Brookline
Photos of the North Portal
The South Portal - 1940s
Remodeling Plans for South Interchange - 1957
Graphic Showing the New South Interchange - 1999
Reconstruction of South Interchange - 1999
History of Saw Mill Run Road

If anyone has articles or photos relating to the history of the Liberty Tunnels or the Liberty Bridge and would like to share this information, please contact us at history@spdconline.org.