Rachel Carson Bridge
Backstory and Context
The first bridge that crossed the Allegheny River where the Carson Bridge now stands was a wooden, covered toll bridge that was built in 1839 and designed by Sylvanus Lothrop. This toll bridge, known as the Hand Street Bridge, was designed for pedestrian and carriage traffic and was replaced in 1890 due to its inability to handle the weight of the newly arrived electric trollies. This second bridge was a steel Pratt through truss bridge designed by George Ferris (of Ferris wheel fame) and Gustave Kaufman.
Shortly after World War I, the War Department established new guidelines for the nation’s bridges in terms of weight capacity, width and height. It did so to ensure that bridges deemed vital could handle the weight of military hardware and that they were high enough to permit passage of necessary supplies on the waterways below. In order to meet those requirements, Pittsburgh’s 6th, 7th and 9th Street Bridges all had to be replaced and the American Bridge Company of New York was tasked with designing both functional and aesthetically pleasing structures.
Their engineers, inspired by a German bridge over the Rhine River in Cologne, developed a unique design and construction method due to the unstable soil along the Allegheny River. Typical suspension bridges drape massive cables on large towers and anchor them to the shore with huge concrete structures. However, this option was unavailable to the designers of the Three Sisters. As a result, they used a self-anchoring system and utilized eye-bars rather than steel cables to hang the bridge deck. These eye-bar chains also drape over the bridge’s towers. However, they are not anchored to the shore, but to the bridge deck’s stiffening girder. The designers then hung the bridge deck on eye-bars of varying lengths that are tied to the bridge’s catenaries or eye-bar chains.
The bridge was renamed to honor Rachel Carson primarily due to the lobbying efforts of Esther Barazzone, the then President of Chatham University, Carson’s alma mater. Carson, who penned numerous books, to include 1962’s Silent Spring which is credited with initiating the modern environmental movement, was born 15 miles upriver from the bridge that now bears her name, in the Pittsburgh suburb of Springdale. She grew up on the family’s 65-acre farm, now the Rachel Carson Homestead, and graduated from the Pennsylvania College for Women with a degree in biology. She then worked for the U.S. Bureau of Fisheries while also writing. She was posthumously awarded the Presidential Medal of Freedom by President Carter in 1980, 16 years after her death.
"Rachel Carson Bridge." PGH Bridges. Accessed May 16, 2017. http://pghbridges.com/pittsburghW/0584-4477/ninth_st_br.htm
"Historic American Engineering Record -- 'Three Sisters' Bridges." PGH Bridges/National Park Service. Accessed May 16, 2017. http://pghbridges.com/articles/haer/sisters_HAER_PA490/sisters_HAER490.htm
Kirkland, Kevin. "The Bridges of Pittsburgh: Rachel Carson Bridge." Pittsburgh Post-Gazette. July 21, 2013. Accessed May 16, 2017. http://www.post-gazette.com/ae/art-architecture/2013/07/21/The-Bridges-of-Pittsburgh-Rachel-Carson-B...