Information page on pghbridges:
view page - Liberty Bridge 1928
Historic American Engineering Record
HAER No. PA-448
Pennsylvania Historic Bridges Recording Project
Spanning Monongahela River at State Rt. 3069
XEROGRAPHIC COPIES OF COLOR TRANSPARENCIES
WRITTEN HISTORICAL AND DESCRIPTIVE DATA
HISTORIC AMERICAN ENGINEERING RECORD
National Park Service
1849 C Street, NW
Washington, DC 20240
HISTORIC AMERICAN ENGINEERING RECORD
HAER No. PA-448
Location: Spanning Monongahela River, E. Carson St., and Second Ave. at
State Rt.3069, Pittsburgh, Allegheny County, Pennsylvania.
USGS Quadrangle: Pittsburgh East, Pennsylvania (7.5-minute series, 1993).
UTM Coordinates: 17/585150/4478380
Dates of Construction: 1925-28
Designers: Allegheny County Department of Public Works: Vernon R. Covell, chief bridge engineer; George S. Richardson, design engineer.
Builders: Dravo Contracting Company and Vang Construction Company, substructure; Independent Bridge Company, superstructure.
Present Owner: Pennsylvania Department of Transportation.
Present Use: Vehicular bridge.
Significance: This 2,663'-0", sixteen-span, $3.7 million Pratt deck truss bridge was the longest and most expensive bridge built in Allegheny County when it was completed in 1928. The bridge features two 450'-0" cantilevered main spans with suspended sections over the Monongahela River and deck girder approach spans on either side. The bridge links Pittsburgh's downtown area with the Liberty Tunnels, built through Mt. Washington in 1924. The opening of the tunnels and the bridge were instrumental in the development of Pittsburgh's South Hills suburbs. The Liberty Bridge was listed in the National Register of Historic Places in 1988.
Historian: J. Philip Gruen, August 1997.
Project Information: This bridge was documented by the Historic American Engineering Record (HAER) as part of the Pennsylvania Historic Bridges Recording Project - I, co-sponsored by the Pennsylvania Department of Transportation (PennDOT) and the Pennsylvania Historical and Museum Commission during the summer of 1997. The project was supervised by Eric DeLony, Chief of HAER.
HAER No. PA-448
The city of Pittsburgh is noted for its phenomenal collection of bridges. These bridges, spanning the Allegheny, Monongahela, and Ohio rivers, have not only been instrumental in stimulating and maintaining Pittsburgh's growth, but their intricate steelwork has contributed to the city's image as an industrial metropolis where the steel industry reigned and coke was king. 
This image is created largely by the total ensemble of bridges. Because so many of them today resemble one another in appearance, only a handful -- particularly Gustav Lindenthal's Smithfield Street Bridge (1883) -- actually stand out. 
Not far to the north of the Smithfield Street Bridge is the Liberty Bridge, little noted today for its engineering significance, less dramatic than some of its neighbors, and hardly noticed by motorists who cannot see the cantilevered deck truss supporting it. Motorists often consider the bridge little more than a conduit transporting them into the Liberty Tunnels toward their bedroom communities in the South Hills.
Yet, as a connection to the South Hills, the Liberty Bridge is enormously important and has had a significant impact on the development of the Pittsburgh metropolitan area. The 2,663'-0"-long, sixteen-span bridge, completed in 1928, helped open up Pittsburgh's sparsely populated South Hills area to extensive development. While settlement and development of the South Hills had begun before the construction of the Liberty Bridge and Liberty Tunnels, the area's development dramatically accelerated once these structures made it easily accessible by automobile. Immediate growth occurred in the old trolley suburbs of Mt. Lebanon, Dormont, and Brookline, whose residents had encouraged the bridge's construction. But the convenient automobile access from the South Hills to downtown ultimately pushed development further out to areas that are examples of early American automobile suburbia: West Mifflin, Pleasant Hills, Bethel Park, and Upper St. Clair.  Many relics from this early phase of suburban automobile America are still in use today.
It is pointless to debate whether the bridge or the tunnel had a greater impact upon the area's development. Both certainly played a part, and the story of one cannot be properly told without that of the other. Considering that many elements of suburban America today (shopping centers, cul-de-sacs, mass-produced homes, and a cloverleaf traffic interchange) were built in the
1] Pittsburgh's steel industry had virtually disappeared by 1997, when this essay was written.
2] This was not always the case. For example, for much of the late nineteenth and early twentieth centuries, where the essentially similar Fort Pitt and Fort Duquesne bridges span the Monongahela and the Allegheny today, were the Point Bridge (a suspension bridge) and the Union Bridge (a wooden covered span) See also U. S. Department of the Interior, Historic American Engineering Record (HAER) No. PA-2, "Smithfield Street Bridge," 1974, Prints and Photographs Division, Library of Congress, Washington, D.C.
3] It is difficult to determine what was America's "first" automobile suburb, although the Bronx River Parkway opened up development in Westchester and Nassau Counties in New York as early as 1921. Philadelphia's Delaware River (now Benjamin Franklin) bridge, completed in 1926, opened up the New Jersey side as an extension of Philadelphia, and New York's Holland Tunnel (1927) opened up New Jersey's northeastern shore. See U.S Department of the Interior, HEAR No. NY- 161,"Holland Tunnel," 1987, Prints and Photographs Division, Library of Congress, Washington, D.C.
LIBERTY BRIDGE HAER
South Hills as early as the late 1920s and '30s, the development of this area is one of the most interesting stories that followed construction of the Liberty Bridge. While the completion of the bridge had an immediate effect on the lessening of traffic problems throughout the city, its far reaching influence in terms of suburban development has arguably been the bridge's most significant contribution to the Pittsburgh area. 
The Liberty Bridge, however, does not lack engineering significance or an important place in American bridge building history. In 1928, the bridge was the largest, highest, and most expensive bridge built in Allegheny County. Its 420'-0" main spans are not only extraordinarily long, but are cantilevered from stately concrete piers resting on concrete footings encased in stone The bridge's construction included a complex approach system on the north side which lifted the bridge above Second Street and the tracks of the Baltimore and Ohio Railroad, with a central ramp that passed underneath the Boulevard of the Allies and connected with Forbes Street. Ramps were added later to link the Boulevard of the Allies directly to the bridge. When the bridge was completed in 1928, a traffic circle with a commemorative monument articulated the southern approach, and a decorative wrought-iron railing with shell motifs and wrought-iron lighting fixtures adorned the roadway's length.
Nevertheless, it has either been the view from the Liberty Bridge to other bridges and to Pittsburgh's downtown skyline, or the processional experience from the city into the tunnels, that has largely colored motorists' impressions of the bridge over the years. By the late 1920s, Pittsburgh's downtown area, riding on the strength of its booming steel industry, featured a compact and distinct downtown district of new high-rise buildings. The city already had numerous bridges spanning its rivers; in fact, the construction of bridges in Pittsburgh has been a vital and constant part of its history. Since 1820, when the first span across the Monongahela River was constructed at the site of the present-day Smithfield Street Bridge, 376 bridges had been built in Allegheny County and "hundreds of others" in the Pittsburgh area. 
Even with numerous bridges already spanning the Monongahela River in the 1910s, including the South Tenth Street Bridge not far north of the Liberty Bridge's proposed site, there was still no convenient automobile access from the edge of the downtown district to the South Hills. The only access to the South Hills by automobile was via the circuitous Brownsville and South Sixteenth Street roads winding up and around Mt. Washington. This spurred residents of the South Hills, in the late 1900s, to suggest the construction of a bridge and tunnel from Pittsburgh's downtown area directly into the South Hills.
4] Today, traffic is regularly backed up along the bridge during rush hour.
5] "The Opening of the Liberty Bridge," Fort Pitt Pointers (1 Apr. 1928), vertical files, Allegheny County Office of Records Administration, Pittsburgh, Pa.
LIBERTY BRIDGE HAER
The lack of access to the South Hills and numerous other infrastructure problems encouraged the Pittsburgh Committee on City Planning in 1901 to hire Frederick Law Olmsted to draft a report on possible civic thoroughfare improvements. Olmsted's 165-page report, among a variety of other things, recommended a new "fast-moving" road along the waterfront (later built as the Boulevard of the Allies) and a bridge-and-tunnel scheme connecting to the South Hills. While the report pondered the possibility of another hillside road, Olmsted recommended the bridge-and-tunnel plan because it provided the most direct access to the South Hills area. He noted the importance of settling the "sparsely populated" South Hills, for it was largely free from pollution yet still quite close to the business district. He correctly predicted that the overwhelming majority of Pittsburgh area residents would eventually live in the hills rather than the valleys closer to the city. 
Olmsted's report favored one particular bridge-and-tunnel scheme, which was then proposed in the late 1900s by South Hills residents. This scheme proposed a road starting from Forbes Street at Sixth Avenue, rising to the bluff north of Second Avenue, and rising again to a new double-decker bridge over the Monongahela River. After crossing the river, the road would continue to rise at the same gradient as it entered a tunnel leading through Mt. Washington to the junction of Washington Avenue and Haberman Street in the South Hills.
With Olmsted's recommended uniform gradient of 3.5 percent, stretching from Forbes Street in the Point District to Washington Avenue on the north side of the South Hills, the tunnels would have been 80'-0" above the Liberty Tunnels' current location. Olmsted suggested this plan rather than a longer, lower bridge-and-tunnel plan (which was eventually adopted) because he felt the higher drop-off point for the tunnels would more easily facilitate the residential development of the uplands areas of Mt. Lebanon and Beechview (lower areas would be accessible via the Sawmill Run Road). In other words, the high-level plan, according to Olmsted, would have not only provided access to those areas that could be reached by a low level bridge-and-tunnel scheme, but would have also provided convenient access to the "more important lands" on the hills that were not easily accessible via the low-level plan. The high-level plan, apparently, would have also been less expensive because it would have required a shorter tunnel. The high-level plan, however, was eventually abandoned because of the heavy grade and the height of the bridge it required. 
6] Frederick Law Olmsted, Pittsburgh: Main Thoroughfares and the Downtown District: Improvements Necessary to Meet the City's Present and Future Needs (Pittsburgh: Pittsburgh Civic commission, 1911), 49-56.
7] Olmsted, Pittsburgh, 55. The high-level plan discussed by Olmsted was originally called the Haberman Tunnel Plan and conceived in 1908 or 1909 by Herrmann Laub and F. I. Gesser. Throughout the 1910s, a number of other tunnel projects were offered, although none of them were proposed in conjunction with bridges See Pittsburgh Department of Public Works, Bureau of Bridges, Description of the Liberty Tunnels, Power Plant, and Bridge, vertical files, Allegheny County Office of Records of Administration, Pittsburgh, Pa.
HAER No. PA-448
Olmsted's recommendations -- or any major civic improvements -- were forced to wait on account of World War I. In 1919, however, the Allegheny County Commissioners proposed a $35.5 million bond issue to be placed on the 2 November ballot that would have allocated over two-thirds of its funding toward bridge construction. Part of this allocation would have included funds for the construction of the Liberty Bridge. The county rescinded its proposal prior to the election, however, in part because of rising opposition to the wording of the proposal, which included funding for a series of other bridges apparently not desired by the citizenry. Another similar bond issue failed in 1921.
The 1924 Bond Measure and the Public Works Department
In 1924, new county commissioners took over and the County Department of Public Works was reorganized. Norman F. Brown, appointed director of the Department of Public Works, helped to redraft the bond measure, now pared from $35.5 million to $29.207 million. This included a $3.771 million allocation for the Liberty Bridge. To help promote the bond measure, the Department of Public Works put together a booklet entitled "Forward or Backward?," arguing that infrastructure improvements permit a "natural forward step" that can save lives and improve living conditions generally. The booklet noted that the Liberty Tunnels, which were nearing completion, would not be exercised to their fullest potential without their "sister," the Liberty Bridge:
(The Liberty Tunnels) are performing but a small percentage of their usefullness [sic.] owing to the absence of a bridge over the Monongahela River connecting these tubes with the city proper and permitting of uninterrupted traffic between the South and other points in the county.... As long as the Liberty Bridge remains unconstructed [sic.], we can hope to enjoy but part of the advantages of the Liberty twin tunnels. Full returns are not being obtained on this investment. 
The measure finally passed on 22 April 1924. 
The plans for the bridge were to be executed under the direction of Vernon R. Covell, chief bridge engineer for the Department of Public Works. Covell, who had served as assistant county engineer from 1897 to 1903 and as deputy county engineer in charge of bridge maintenance from 1906 to 1922, was appointed county engineer in charge of design, erection, and maintenance of county bridges (and alterations to and construction of county buildings) on 16 October 1922. The reorganization of the county offices in 1924 gave him a new position as the chief engineer of bridges.
8] Pittsburgh Department of Public Works, Forward or Backward?, 1924, vertical files, Allegheny County Office of Records Administration, Pittsburgh, Pa.
9] The political machinations involved in the passage of the bond measure and other details pertaining to the Allegheny County Department of Public Works at this time are detailed in Peter M. Earrington, "The Allegheny County Highway and Bridge Program 1924-1932,'' Master's thesis, Carnegie-Mellon Univ., 1982.
HAER No. PA-448
It is unlikely, however, that Covell had much to do specifically with the design of the Liberty Bridge. In his memoirs, former Allegheny County bridge engineer George S. Richardson, who would go on to design the McKee's Rocks, Homestead High Level, Westinghouse Memorial, West End, Fort Pitt, and Fort Duquesne bridges, among others, noted that in late 1924 or early 1925, he was actually placed in charge of design for the new Point Bridge and the proposed Liberty Bridge. Richardson, a 28-year-old draftsman at the time, recalled that his own ability to manage loads on statically indeterminate structures at an early stage in his career was the reason he was given greater responsibilities within the department.  He pointed out that Covell "did not participate in any way in the selection of type of structures for any of the bridges or any of the supervision or design of the selected type." Richardson did not recall Covell showing any particular interest in any phase of the design work for county bridges except for the railings to be used on the bridges. 
By August 1924, however, neither Richardson nor anybody else in the Public Works Department had begun working on the Liberty Bridge plans -- apparently because the issue of the bridge's northern approach had not been settled. One plan, proposed by the Department of Public Works, favored a two-level approach: one level linking with the Boulevard of the Allies and the other passing under the boulevard and terminating at Forbes and Shingiss Streets. The other plan, offered by the City Planning Commission, suggested terminating the approach at Second Avenue and Ross Streets. Nevertheless, by December 1924, despite lacking final approval for the approach, work had begun on the drawings.
The plans for the two-level northern approach included a provision to carve away the bluff along Shingiss Street and build a large, sloping reinforced concrete retaining wall to protect it. The river spans, originally planned as arches, were changed to cantilevers in order to comply with clearance requirements set forth by the U. S. Army Corps of Engineers. The original plans apparently would have obstructed navigation, and all bridges built over navigable waterways in the United States had to provide enough clearance, both vertical and horizontal, to comply with
10] Richardson explained that from 1924 onward, he was given "complete responsibility for estimates, supervision of all superstructure designs, preparation of contract plans, checking of erection and shop drawings for all of the remaining 1924-28 programs. See George S. Richardson, "History of Allegheny County Bridges," 14 Aug 1979, prepared for Steven J. Fenves, professor of Civil Engineering, Carnegie-Mellon Univ., vertical files, Pittsburgh History and Landmarks Foundation, Pittsburgh, Pa.
11] Richardson, "History of Allegheny County Bridges," 5.
HAER No. PA-448
the federal codes.  The cantilever design allowed for the construction to proceed without the aid of a channel-obstructing falsework. 
On 31 January 1925, Congress passed an act granting Allegheny County permission to build the bridge.  The petition for a "public bridge ... across the Monongahela River, extending from the Liberty Tunnels, at Brownsville Avenue, to Forbes Street, in the City of Pittsburgh," was adopted by the Allegheny County Commissioners on 20 April 1925, and by the grand jury on 7 May 1925.  On May 24, a permit was issued by the U.S. War Department to begin construction, and the Allegheny County commissioners immediately began advertising for bids. 
On 7 July 1925, the Dravo Contracting Company was given permission to begin work on the substructure. The superstructure, however, was delayed because of complications again rising from the northern approach's proposed location. The situation was cleared up in October of 1925 and work proceeded. By the end of the year, erection of the masonry piers and approaches was well underway. In September 1926, approximately 500 feet of the steel had been erected and a local newspaper predicted completion by September 1927.  In June 1927, the superstructure was finished and work on the troublesome northern approach was the only major part of the bridge awaiting completion. By March 1928, however, the project was complete and the bridge was ready to be thrown open to traffic.
A grand opening celebration was held on the bridge on 27 March 1928, featuring a five mile-long procession of cars, bands, floats representing organizations from every borough and township in the South Hills, and many county and civic officials. The parade began at Castle Shannon and Washington roads in Mt. Lebanon and passed through Dormont, Brookline, and Allentown before heading across the Smithfield Street Bridge, where it wound from Fifth Avenue to Sixth Avenue before proceeding onto the bridge. The parade concluded at the southern end of the bridge, just before the Liberty Tunnels, where city and county officials gave
12] "Plans for Liberty Bridge Changed to Meet Objections," Pittsburgh Post-Gazette (1 Feb.1925); U.S. Statutes of Large 34 (1911),84-6.
13] A photograph taken of the Liberty Bridge during construction depicts this process nicely; see Joseph White and M. W. von Bernewitz, The Bridges of Pittsburgh (Pittsburgh: Cramer Printing and Publishing Company, 1928), 4.
14] U.S. Statutes at Large 43 (1911), 802-3. This act, however, did not specify the bridge's exact location, but said it would be built "one and two-tenths miles" from the Monongahela's confluence with the Allegheny.
15] Allegheny County, Pennsylvania, Road Docket Court of Quarter Sessions No. 2, Apr.1925.
16] "Liberty Tunnel Plans Approved by War Office Engineers," Pittsburgh Post-Gazette (27 May 1927).
17] "Liberty Bridge Work is Speeded," Pittsburgh Telegraph (15 Sep.1926).
18] An article printed after the opening noted that the floats in the procession represented "practically every business house in the South Hills." see "Five-Mile Parade Marks Opening of Liberty Span," Pittsburgh Post Gazette (28 Mar. 1928), 1.
HAER Text: J. Philip Gruen, August 1997; Pennsylvania Historic Bridges Recording Project - I
visit site - "American Memory" at Library of Congress
visit site - National Park Service -- Historic American Engineering Record