The Three Sisters Bridges

The Three Sisters Bridges (HM1ER3)

Location: Pittsburgh, PA 15222 Allegheny County
Country: United States of America

N 40° 26.683', W 80° 0.075'

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Inscription

Three Rivers Heritage Trail

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 engineering and technology.
Details
HM NumberHM1ER3
Tags
Placed ByFriends of the Riverfront, Pennsylvania DCNR, Steel Industry Heritage Corporation, City of Pittsburgh, FUZE
Marker ConditionNo reports yet
Date Added Friday, September 19th, 2014 at 11:52pm PDT -07:00
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Locationbig map
UTM (WGS84 Datum)17T E 584698 N 4477597
Decimal Degrees40.44471667, -80.00125000
Degrees and Decimal MinutesN 40° 26.683', W 80° 0.075'
Degrees, Minutes and Seconds40° 26' 40.98" N, 80° 0' 4.50" W
Driving DirectionsGoogle Maps
Area Code(s)412, 724, 215
Closest Postal AddressAt or near 111-121 10th Street Bypass, Pittsburgh PA 15222, US
Alternative Maps Google Maps, MapQuest, Bing Maps, Yahoo Maps, MSR Maps, OpenCycleMap, MyTopo Maps, OpenStreetMap

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