Three Sisters (Pittsburgh)
three very similar bridges in downtown Pittsburgh, Pennsylvania, United States
The Three Sisters are three similar self-anchored suspension bridges spanning the Allegheny River in downtown Pittsburgh, Pennsylvania at 6th, 7th, and 9th streets, generally running north–south. The bridges have been given formal names to honor important Pittsburgh residents:
Roberto Clemente (Sixth Street Bridge)
Andy Warhol (Seventh Street Bridge)
Rachel Carson (Ninth Street Bridge)
Designed by the Allegheny County Department of Public Works, they were all built in a four-year period, from 1924 to 1928, by the American Bridge Company, replacing earlier bridges of various designs at the same sites. Their construction was mandated by the War Department, citing navigable river clearance concerns. They are constructed of steel, and use steel eyebars in lieu of cables.
The Three Sisters are historically significant because they are the only trio of nearly identical bridges, as well as the first self-anchored suspension spans, built in the United States. They are among the only surviving examples of large eyebar chain suspension bridges in America, and furthermore, unusual for their self-anchoring designs. The bridges’ design was viewed as a creative response to the political, commercial, and aesthetic concerns of Pittsburgh in the 1920s.
The bridges were designed under the auspices of the Allegheny County Department of Public Works, by T. J. Wilkerson, consulting engineer; Vernon R. Covell, chief engineer; A. D. Nutter, design engineer; and Stanley L. Roush, architect. The American Bridge Company built the superstructure, while the Foundation Company built the substructure.
All three bridges are owned by Allegheny County.
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This entry incorporates text from “Three Sisters (Pittsburgh)” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.