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Historic American Engineering Record
Smithfield Street Bridge, Pittsburgh (PA-2)


Historic American Engineering Record (HAER)
Heritage Conservation and Recreation Service
Historic American Buildings Survey - Collection of the Library of Congress

Smithfield Street Bridge
PA-2 (LOC call number: HAER, PA,2-PITBU,58-)
Location: Pittsburgh, Pennsylvania; UTM: 17.584630.4476290; Quad: Pittsburgh West
Date of Construction: Completed 1883; Altered 1891
Present Use: Highway Bridge (initial use)
Significance: Designed by Gustav Lindenthal, one of America's most famous bridge engineers, as a two-lane bridge. One lane was erected in 1883, and another was added in 1891. The span is Pittsburgh's most graceful and makes use of a double lenticular truss, patented in America by Edwin Stanley in 1851.
Historian: James D. Van Trump, 1974

A Trinity of Bridges: The Smithfield Street Bridge over the Monongahela River at Pittsburgh

by James D. Van Trump

Pittsburgh's first river bridge -- that over the Monongahela River at what is now Smithfield Street -- is historically speaking three bridges all built successively at the same site by a trinity of famous American bridge engineers, Lewis Wernwag, John A. Roebling, and Gustave Lindenthal, who had all been born in Germany and thus learned their technology from that early and famous fountain of engineering. It was America, however, a new and developing country, that gave them the widest scope for their abilities, and Pittsburgh with its great need for bridges was a special beneficiary of their knowledge, as it was a showcase for their talents.

This essay is a study, therefore, of the three versions of the bridge erected at Smithfield Street as well as a consideration of the development of the technology of bridge construction during the nineteenth century.


From the foundation of the first settlement at Pittsburgh until 1818, the only means of communication between and the further banks of the rivers was by canoe or skiff. As settlement developed a ferry service became mandatory, and in 1818 Jones' Ferry operated between the mouth of Liberty Street in Pittsburgh and the south bank of the Monongahela. Passengers were carried in skiffs while stock was taken on flat boats. About 1840 a horse ferry was introduced. Blind horses, as a rule, were made to tramp upon a horizontal wheel, the revolution of which propelled the boat across the stream.

A few years later Captain Erwin established a steam ferry from a site on the south bank of the Monongahela slightly below the confluence of the rivers at the Point, but this was never a success. (1) Subsequently the Jones' Ferry was abandoned, and a steam ferry operated from Saw Mill Run on the south bank of the Ohio to Penn Street in Pittsburgh. This line was in use until the increasing number of river bridges made it redundant. (2)

Prior to the building of the Monongahela Bridge, all traffic passing from side of the river to the other at Smithfield was carried on a little ferry boat owned by Enoch Wright of Westmoreland County and Andrew Herd of Allegheny County, who leased the buildings, ferry, and improvements to one Robert Shanhan. Where the ferry landed on the South Side stood Enoch Wright's stone house. After the bridge was constructed the ferry rights were bought out by the Stock Company. (3) Before the introduction of dams toward the end of the nineteenth century, the streams at slack water were relatively shallow and numerous islands and sand bars were in evidence. There was, for instance, a long sand bar in the Monongahela River at the site of the Smithfield Street Bridge. (4) This river flat land that is shown on the very early maps of Pittsburgh, was of sufficient extent that grain could be grown on it at low water. It must be remembered also that there was extensive traffic on all three rivers and the spans of bridges had to be sufficiently high to allow boats to pass beneath them.

Monongahela Bridge, 1818

The first of Pittsburgh's highway river bridges was the Monongahela (later Smithfield Street) Bridge. Erasmus Wilson, a late nineteenth century historian of Pittsburgh, has left the best account of its construction and we quote it here: (5)

"In the year 1810 a bill was introduced in the (Pennsylvania) State Legislature providing for the construction of two bridges at Pittsburgh -- one over the Monongahela and one over the Allegheny -- and an estimate of the probable cost of such a structure was made by Judge Findley. It was calculated by him that the 1,200 feet of river would require chains of 1,590 feet and four such chains of inch and a half square iron bar weighing sixty-four pounds to the foot, with some excess, would amount to $8,800; smith work would cost $3,080; a bridge thirty feet wide would require $900,000 worth of plank; three piers would cost $15,000; other expense, $1,050; right to use certain patents, $1,200; putting together, $1,296; incidentals, $1,000; total $32,326. James O'Hara, William McCandless, David Evans, Ephraim Pentland, Jacob Beltzhoover, Adamson Tannehill, Thomas Cromwell, Thomas Enochs, and Dr. George Stevenson, were the commissioners appointed to open books for the subscription of stock in the Monongahela Bridge. John Wilkins, James Robinson, Nathaniel Irish, George Shiras, George Robinson, Issac Craig, James Irwin, John Johnston, and James Riddle, were authorized to open books for the subscription of stock in the Allegheny Bridge. (6) Probably owing to the War of 1812, the bridges were not built at that time and in 1816 the law was re-enacted (7) and the governor, on behalf of the State, was authorized to take 16,000 shares of stock in each bridge. The law specified that one was to be built over the Monongahela at Smithfield Street and one over the Allegheny at St. Clair (now Sixth) . . .

"The last installment of stock for the Monongahela Bridge was called for by treasurer, John Shaw, to be paid May 15, 1818. The first arch was laid on the piers on Saturday, June 20, 1818. (8) The bridge was rapidly built once it was begun and it rested on two abutments and seven intermediate piers of stone. It was constructed of wood and iron, with the catenarian curve of arches, the contract price being $110,000. As if to favor the contractors the weather during the fall was excellent.

"The beautiful bridge over the Monongahela has nearly reached the northern shore; it will probably be crossed before Christmas. The one over the Allegheny is not so far advanced, but yet enough is done to ensure its completion. Pittsburgh will then exhibit what no American city or town has ever yet done -- two splendid bridges over two mighty streams, within 400 yards of each other. (9)

"On Saturday (November 21, 1818) the last arch of the Monongahela being completed, and the whole floored, the undertakers and builders announced the pleasing event by the discharge of cannon from the middle pier and the display of the United States flag waving over the central arch, having attached to its staff a beautiful banner with appropriate representations. The City Guards and the new company of Washington Guards from Birmingham heralded on their respective sides of the river, marched across and fired salutes. In the afternoon the workmen sat down to a substantial dinner, at which Mr. Johnston, the meritorious undertaker and superintendent, presided . . .

"November 26, 1818, John Shaw, treasurer of the Monongahela Bridge Company, called a meeting of the managers to appoint a gatekeeper to receive the toll as follows: Foot passengers, 2 cents; vehicles of four wheels and six horses, 62-1/2 cents; vehicles of two horses, 25 cents; vehicles of one horse, 20 cents; horse and rider, 6 cents; horse alone, 6 cents; each head of cattle, 3 cents; each head of sheep, 3 cents.

"The State held $40,000 worth of stock in the Monongahela Bridge and was required to assist in repairing the damage caused by the falling of (part of) the span in 1831-32."

Monongahela Bridge Description and Fire

Llewellyn Edwards describes the Monongahela Bridge as follows: "The substructure consisted of two abutments and seven piers of stone masonry. The superstructure had eight covered wood truss spans and an overall length of 1500 feet." (10)

Richard Allen also comments on both the Monongahela and Allegheny Bridges (the latter not finished until 1819). The Monongahela was a Burr truss structures and Allen states that -- "Its outstanding feature was the toll collector's living quarters. He was housed in a small apartment built above the barn-like portal of the Pittsburgh side." (11)

The Burr truss which appears so frequently in the chronicles of early American bridge construction, was named for Theodore Burr (1771-1822), a well known bridge designer of his day. Like all his contemporaries, he, for all but very short spans, combined the arch and truss (witness the "catenarian arches" of the Gazette account quoted earlier), but instead of combining them by strengthening the arch by the truss, as did the rest, he strengthened the truss by the arch. His design was in reality merely a series of king posts and it is safe to say that the majority of wooden covered bridges built in the United States were of the Burr truss design. (12)

The designer of both the Monongahela and the Allegheny Bridges was Lewis Wernwag (1769-1843) who was perhaps the most famous of all early American bridge engineers. Born in Germany he came to the United States at the age of seventeen, settling in Philadelphia. He specialized in wooden truss spans, his first famous work being a bridge of a single span constructed in 1812 over the Schuylkill River at Philadelphia. He later constructed many highway and railroad bridges. A letter from his son John to Samuel Smedley published in Engineering News, August 13, 1885, includes a list of twenty-nine bridges built by his father during his active career of twenty-seven years. (13) Of all these bridges the Monongahela was not the least famous.

Joseph H. Thompson was the builder of the Monongahela Bridge and a contract was made with him on July 9, 1816 to construct Wernwag's "double-passage bridge covered from end to end." The contract price was $110,000. (14)

The Monongahela span gave many years of good service to the developing Pittsburgh region but it disappeared in ten minutes in a long trailing line of smoke and flame at two o'clock in the afternoon during the Great Fire of April 10, 1845, (15) one of those huge conflagrations that devastated American cities in the nineteenth century. (16) At the time of its destruction it was still the only bridge over the Monongahela at Pittsburgh.

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Last modified: 30-Sep-1999

Historic American Engineeering Record (HAER) Text: James D. Van Trump, 1974