English: The source of the Ohio River at “The Point” in Pittsburgh, Pennsylvania, USA. The Allegheny River (left) and the Monongahela River (right) join to form the Ohio here. The West End Bridge crosses the Ohio in the foreground. (Photo credit: Wikipedia)
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.
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.
Read more: http://www.post-gazette.com/stories/life/lifestyle/pittsburgh-bridges-a-showcase-of-engineering-ingenuity-696224/#ixzz2ZfxMNSfF