Modern bridges are super-sized paths of steel with carpets of concrete that soar through the air.
As tour de forces of design, engineering and teamwork, bridges are our most functional visible form of public art. These sturdy structures afford us breathtaking views of the region while stoking our sense of optimism. From their portals, we cross deep ravines, wide valleys and rivers, especially rivers.
With a total of 446 bridges, Pittsburgh is a permanent showcase of inspired engineering. Its rugged topography has made it a hotbed of bridge design since the city was named in 1758, and the region's hills and geological formations afforded the natural resources, including wood and stone, to build the bridges needed to connect it.
David McCullough: Bridges of the Allegheny
Author, historian and Pittsburgh native David McCullough narrates a look at the bridges spanning the Allegheny River. (Video by Andrew Rush; 7/21/2013)
The city's first span, opened in 1818, crossed the Monongahela River on the site of the current Smithfield Street Bridge. The first Sixth Street Bridge spanned the Allegheny River just a year later, ushering in a generation of covered wooden bridges. Until the late 1800s, everyone -- whether in a horse-drawn wagon or on foot -- paid tolls to cross the city's major bridges. We still pay today -- our tax dollars fund multimillion-dollar PennDOT projects.
John Augustus Roebling, the best-known civil engineer in America, designed three local bridges -- an aqueduct across the Allegheny River for the Pennsylvania Canal and the second versions of the Sixth Street and Smithfield Street bridges. As part of the next leap forward in bridge-building technology, he perfected the use of wire cable in suspension bridges here before designing his masterpiece, the Brooklyn Bridge.
Pittsburgh's industries and resources have continued to support its bridges. When steel and concrete became the preferred building blocks, abundant supplies of coal, sand and gravel aided in the production of those two materials. In the first half of the 20th century, ironworkers used hot rivets to weld steel plates together.
Pittsburgh and Allegheny County's golden age of bridge building began in the 1920s, when the county spent $24 million to build 43 bridges and a city art commission insisted that they be beautiful as well as functional.
In the second half of the 20th century, advances in the fabrication of steel box-girders made it easier to build longer bridges, and computers aided manufacture and design. The Fort Pitt and Fort Duquesne bridges, which opened in 1959 and 1969, respectively, were among the first created with the help of a computer.
Today, when civil engineers gather, three of their annual awards bear the names of men who left their stamp on Pittsburgh's bridges: Roebling, Gustav Lindenthal and George Richardson. Lindenthal took a figure eight and turned it on its side to create what is perhaps Pittsburgh's best-loved design -- the Smithfield Street Bridge of 1883. Richardson, the dean of Pittsburgh bridge engineers, designed the Fort Pitt, Fort Duquesne, McKees Rocks, West End, Homestead Grays and George Westinghouse Memorial bridges.
The region's bridge builders are also famous names. The Union Bridge Co., Fort Pitt Bridge Works and American Bridge Co., after which the Beaver County town of Ambridge was named, built bridges here and around the world.
Increasingly, the bridges themselves bear names and not just of the streets or towns they connect. On Saturday, the 31st Street Bridge across the Allegheny was renamed for Vietnam War hero William R. Prom of Reserve. Now, every major bridge on that river from the Point to Washington's Crossing at 40th Street is named for someone, giving us the chance to take another look at the magnificent structures that make our daily lives easier in so many ways.
Websites www.pghbridges.com and www.BridgeMapper.com, "Pittsburgh's Bridges" by Walter C. Kidney, "The Bridges of Pittsburgh and Allegheny County" by Robert J. Gangewere, "The Bridges of Pittsburgh" by Joseph White and M.W. von Bernewitz, "The Bridges of Pittsburgh" by Bob Regan, Pittsburgh Press/Pittsburgh Post-Gazette archives.
First Published July 21, 2013 4:00 AM