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MARKER DATABASE
“Bite-Size Bits of Local, National, and Global History”
“Bite-Size Bits of Local, National, and Global History”
Pittsburgh in Allegheny County, Pennsylvania — The American Northeast (Mid-Atlantic)
 

The Three Sisters Bridges

Three Rivers Heritage Trail

 
 
The Three Sisters Bridges Marker image. Click for full size.
By Mike Wintermantel, June 5, 2014
1. The Three Sisters Bridges Marker
Inscription. The three identical bridges spanning the Allegheny River are the only known example of a triple set of bridges constructed side-by-side across a major river. They were built between 1926 and 1928 when the War Department ruled that bridges over Pittsburgh's rivers had to be high enough not to interfere with river commerce in steel, coal and war materials during times of war.

Their design is unique. They are self-anchoring suspension bridges-standing firmly on piers in the river and extending stiff girders out to meet the banks-but they are not anchored to the land. Their rigid eyebar chains are suspended from central towers and fastened to the end of giant girders that hold up the roadway.

In 1926 the City Art Commission influenced the design of the first bridge, the Seventh Street Bridge, which was based on a rare example in Cologne, Germany. Pittsburgh's American Bridge Company built the bridge. The design reflected the Art Deco architectural style of the period. Within two years, identical spans were erected at Ninth and Sixth Streets.

In 1928, The American Institute of Steel Construction voted the Sixth Street Bridge, now called the Roberto Clemente Bridge, the "most beautiful bridge" built in America that year. The Three Sisters are listed on the National Register of Historic Places for their significant
The Three Sisters Bridges Marker image. Click for full size.
By Mike Wintermantel, June 5, 2014
2. The Three Sisters Bridges Marker
Looking west towards the Roberto Clemente (6th Street) Bridge
engineering and technology.
 
Erected by Friends of the Riverfront, Pennsylvania DCNR, Steel Industry Heritage Corporation, City of Pittsburgh, FUZE.
 
Location. 40° 26.683′ N, 80° 0.075′ W. Marker is in Pittsburgh, Pennsylvania, in Allegheny County. Marker can be reached from the intersection of Fort Duquesne Boulevard and 7th Street. Touch for map. Sign is mounted to the railing in Fort Duquesne Boulevard Park. Marker is in this post office area: Pittsburgh PA 15222, United States of America.
 
Other nearby markers. At least 8 other markers are within walking distance of this marker. Seventh Street Bridge (within shouting distance of this marker); Roberto Clemente Bridge (about 500 feet away, measured in a direct line); The Pittsburgh Agreement (about 600 feet away); Ninth Street Bridge (about 700 feet away); Sisters of Mercy (about 700 feet away); The Benedum Center (about 800 feet away); Heinz Hall (approx. 0.2 miles away); Fort Lafayette (approx. 0.2 miles away). Touch for a list and map of all markers in Pittsburgh.
 
Categories. Bridges & ViaductsIndustry & CommerceWaterways & Vessels
 
The Three Sisters Bridges Marker image. Click for full size.
By Mike Wintermantel, June 5, 2014
3. The Three Sisters Bridges Marker
Looking east towards the Andy Warhol (7th Street) and Rachel Carson (9th Street) Bridges
The Three Sisters Bridges Marker image. Click for full size.
By Mike Wintermantel, June 5, 2014
4. The Three Sisters Bridges Marker
Historic photos of the previous bridges
The Three Sisters Bridges Marker image. Click for full size.
By Mike Wintermantel, June 5, 2014
5. The Three Sisters Bridges Marker
Graphic caption:
This photo from 1859 shows the second bridge at Sixth Street designed by famous engineer John Roebling. It was considered to be the most beautiful of his early cable-suspension bridges. Roebling used this bridge on his company letterhead. Also outstanding was the early Seventh Street Bridge (1884), by Gustav Lindenthal, before he designed the present Smithfield Street Bridge.
Carnegie Library of Pittsburgh
The Three Sisters Bridges Marker image. Click for full size.
By Mike Wintermantel, June 5, 2014
6. The Three Sisters Bridges Marker
Left photo:
The existing Sixth Street Bridge replaced Roebling's bridge. Note the partially completed Seventh Street Bridge, built on the site of Lindenthal's bridge.
American Bridge Company

Right photo:
Huge eyebar chains, connected with pins, hold up the deck built on the massive girders.
Carnegie Library of Pittsburgh
 
 
Credits. This page was last revised on June 16, 2016. This page originally submitted on June 5, 2014, by Mike Wintermantel of Pittsburgh, Pennsylvania. This page has been viewed 306 times since then and 30 times this year. Photos:   1, 2, 3, 4, 5, 6. submitted on June 5, 2014, by Mike Wintermantel of Pittsburgh, Pennsylvania.
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