Three rivers - the Allegheny, Monongahela, and Ohio - join in Pittsburgh, making the city a natural site for the building of bridges. But the Smithfield Street Bridge stands apart from other Pittsburgh bridges for several reasons: it replaced structures by two well-known bridge engineers, Lewis Wernwag and John A. Roebling; it was the first use in America of the lenticular - or lens-shaped - truss design; and it was one of the first major bridges in the U.S. built primarily with steel.
Blast Furnace
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Image Credit: Courtesy Flickr/RJ Schmidt (CC BY-ND 2.0)Image Caption: Smithfield Street BridgeEra_date_from: 1883
1975
When erected by Peter Grubb to smelt the rich iron ore of the nearby Cornwall ore banks, this stone-built blast furnace was typical for its time, producing about 20 tons of pig-iron and cast-iron products a week. A major reconstruction in 1856 to 1857 produced important changes: the furnace itself was enlarged; the blast-air bellows were replaced by a pair of wooden cylinder "blowing tubs"; the waterwheel that had powered them was replaced by a 20-horsepower steam engine; and a pair of waste-heat boilers to supply the engine was built into the open stack of the furnace.
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Image Credit: Courtesy Wikipedia/Wherring (CC BY-SA 3.0)Image Caption: Cornwall Iron FurnaceEra_date_from: 1742
1985
These engines, built by Cooper & Co., of Mount Vernon are among the oldest surviving agricultural steam engines to show the evolution from the portable, skid-mounted engine (ca. 1860) to the horse-drawn engine (1875), through the self-propelled but horse-guided engine (1875) and finally to the self-propelled, self-steered traction engine (1883). Such engines powered the conversion to mechanized farming, which was a great hallmark of the Industrial Revolution.
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Image Credit: Courtesy ASMEImage Caption: Cooper Self-Propelled, Self-Steering Traction EngineEra_date_from: 1860s
1998