Pittsburgh is an old and historic city known for its beautiful architecture and its plethora of bridges. But what is the oldest bridge in Pittsburgh?
Pittsburgh’s oldest bridge is the Smithfield Street Bridge. Opened in 1883, the Smithfield is a lenticular truss bridge with multiple traffic lanes and two pedestrian walkways. Although it was nearly demolished in the 1990s, the bridge was reconditioned in 1995 after a heroic effort by local advocates.
How high is the Smithfield Street Bridge? Can you walk across it? Who designed the Smithfield Street Bridge, and how long is it? This bridge is critical to Pittsburgh’s infrastructure; as you continue, you’ll learn the answers to these questions and more.
The History of the Smithfield Street Bridge
Pittsburgh sits at the confluence of the Monongahela, Allegheny, and Ohio Rivers. The city’s location at the meeting point of these major waterways has necessitated building multiple bridges to connect it to other places. The specific site of the Smithfield Street Bridge was one of the first places to be bridged, as it connects downtown Pittsburgh with the lands on the south shore of the Monongahela River.
In 1816, the first bridge across the Monongahela was designed by a German immigrant named Louis Wernwag. In 1786, at the age of 17, Wernwag fled mandatory military service in his native Germany and made his way to Philadelphia. In Philadelphia, he began building small machines, then advanced to mills and bridges. Then in 1816, he was contracted to design a bridge across the Monongahela.
Wernwag’s bridge was a wonder of its time. It spanned 1,500 feet across the river and featured an elegant wood cover and iron structural supports. The Monongahela Bridge, as it was known, was the only direct route to the municipalities south of Pittsburgh. Knowing it would be in high demand, the bridge’s operators required tolls of 2 cents for foot passengers, with higher tolls for horses, carriages, and livestock such as sheep or cattle.
Lovely as it was, the Monongahela Bridge was destined for tragedy. In 1832, the Monongahela Bridge was struck broadside by a runaway riverboat, causing two sections to collapse. The bridge was rebuilt, only to be destroyed in the Great Fire of 1845.
After the fire, a new bridge was designed. The famous engineer John Roebling designed a beautiful suspension bridge using the stone pilings from the original Monongahela Bridge. The Roebling Bridge worked well, but as time went on, increasing traffic across the bridge began to test the limits of the structure. It was time to build a new bridge.
In 1881, an Austrian engineer named Gustav Lindenthal was contracted to build the new bridge. To minimize the disruption from construction, the new Smithfield Street Bridge was actually constructed on top of the active, still-used Roebling Bridge! The new and improved Smithfield Street Bridge was finally opened to the public on March 9, 1883, and has been a staple in Pittsburgh’s infrastructure ever since.
Lenticular Truss Bridges
The Smithfield Street Bridge is a kind of bridge called a lenticular truss bridge. Truss bridges are designed with…well, trusses! A truss is an assembly of beams that connect at specific points to create a rigid structure that then acts like a whole object. A truss takes on a load, such as a bridge deck or a roof, and spreads it across the structure.
A lenticular truss bridge is a bridge that has trusses that are roughly shaped like lenses. This kind of structure is also sometimes called a cats-eye bridge, a pumpkin-seed bridge, or, more abstractly, a kissing-fish bridge, as the lenticular trusses somewhat resemble these objects.
The trusses on top of the lens – called the top chords – handle the compressive or pushing force of the load of the bridge. The trusses on the bottom – called, you guessed it, bottom chords – handle the tension or pulling force of the bridge. These forces balance, supporting the weight of the structure.
While lenticular truss bridges were very popular in Europe and especially in Germany, they were less common in the United States. As a result, there are only about 50 lenticular truss bridges in the United States today.
Lindenthal’s Other Tricks
Building atop a still-used bridge was not Lindenthal’s only architectural trick. As befitting a bridge built in mighty Pittsburgh, the City of Steel, the Smithfield Street Bridge was one of the first in the world to utilize structural steel. It was also designed with expansion in mind, as Lindenthal saw that Pittsburgh was a growing and important city.
This decision proved prescient: by 1911, the bridge had more than doubled in width as lanes were added. As time went on, everyday traffic became heavier, both in terms of how many people used the bridge and how heavy cars and trains were becoming.
Engineers were concerned that the increased loads on the bridge would cause it to wear out and collapse, but rather than replacing such a beautiful bridge, they decided to modernize it.
In the 1930s, many of the bridge’s structural steel elements were removed and replaced with a new aluminum alloy. Using aluminum instead of steel reduced the load on the bridge by almost 750 metric tons.
By 1967, the bridge was once again ready to be refurbished. The structure had been showing signs of significant wear, causing local authorities to place weight limits and restrictions on vehicles crossing the bridge. In addition, advances in metallurgy had led to even lighter aluminum alloys, so more components of the bridge were replaced with lightweight aluminum, and significant portions of the bridge were rebuilt or reinforced.
Keystone Answers Fun Fact: Pittsburgh is named in honor of the 1st Earl of Chatham and British statesman William Pitt.
The Modern Smithfield Street Bridge
By 1994, the bridge was more than 100 years old and in need of even more repair work. Authorities contemplated simply demolishing the bridge and replacing it with a newer, higher, better bridge, but the bridge’s beautiful design and historical significance made it meaningful to the community. The Pittsburgh History and Landmarks Foundation convinced officials to keep the bridge, which was rehabilitated into its most modern iteration.
In 1994 and 1995, workers renovated the bridge. The bridge deck was replaced, and the bridge was given a facelift with new paint and lighting. In addition, the rail lines, disused for decades, were converted into an extra lane for traffic and a special light-controlled bus lane.
Today, the bridge is a heavily-trafficked pedestrian bridge, very popular with commuters and tourists alike. There are lanes for vehicles and two walkways for foot traffic. There have not been tolls on the bridge since 1911, so commuters and pedestrians alike can cross the Smithfield Street Bridge for free!
How High is the Smithfield Street Bridge?
The Smithfield Street Bridge is one of the lowest bridges in Pittsburgh, with a deck height of 42 feet 6 inches. This height makes it one of the lower bridge decks in Pittsburgh. Forty-two feet, however, is still pretty high: the average giraffe stands about 19 feet tall, so the bridge is about two giraffes tall, or the height of one brachiosaurus.
If you prefer a more meaningful comparison, the bridge stands about as tall as a four-story building. And the beautiful brick pilings and trusses, plus its location in front of the Pittsburgh skyline, have made the Smithfield Street Bridge a Pittsburgh icon.
How Long is the Smithfield Street Bridge?
The Smithfield Street Bridge spans about 1,184 feet as it crosses the Monongahela River. Each of the main spans, with their distinctive steel trusses, is 360 feet long. The remainder of the length of the bridge consists of the stubs that connect the shoreline to the trusses.
Can You Walk Across the Smithfield Street Bridge in Pittsburgh?
The Smithfield Street Bridge is very pedestrian-friendly. In fact, it is one of the most popular bridges to walk across in Pittsburgh. Locals walk across the bridge to commute to and from work, and tourists walk across to enjoy the scenic skyline views and the majesty of this old bridge.
There is no toll to cross the bridge. If you want to walk across, there are several parking lots within close proximity of the bridge’s South Shore entrance. The bridge is a very short walk from the Station Square transit station, which connects to Pittsburgh’s more extensive transit network.
If you want to walk across the Smithfield Street Bridge, you can park your car along the South Shore and stroll across the pedestrian walkway. The bridge offers phenomenal views of Pittsburgh’s skyline, so be sure to bring your camera!
Who Designed the Smithfield Street Bridge?
The Smithfield Street Bridge was designed by a man named Gustav Lindenthal. Lindenthal was a civil engineer who specialized in building bridges. In 1881, he was approached to design the Smithfield Street Bridge, and it was he who came up with the iconic design of the bridge’s beautifully curved trusses.
Lindenthal also designed many of Pittsburgh’s other bridges, including the Seventh Street Bridge and the Youghiogheny River Bridge. While he spent much of his career in Pittsburgh, he also designed the Queensboro Bridge and the Hell Gate Bridge in New York City.
Over the Bridge
Pittsburgh is a city of architectural marvels, ranging from Frank Lloyd Wright’s masterful Fallingwater to the industrial-gothic looks of the U.S. Steel Tower to the soaring glass superstructure of PPG Place. But none of these masterpieces are as old or venerable as the Smithfield Street Bridge. With more than 100 years of almost continuous operation under its belt, the Smithfield Street Bridge is the oldest and possibly the most interesting bridge in the City of Pittsburgh.