Cantilever

The bridge is immense, not only in length and weight but in width. At 67 feet wide, it can accommodate two sets of railway tracks, two sets of streetcar tracks and two roadways.

It took three tries and cost 89 lives, but the city of Quebec was determined to compete with provincial rival Montreal for commercial rail traffic in the late 19th century. The solution was a rail bridge across the St. Lawrence River requiring a single cantilever span 1,800 feet long - the longest ever attempted. 

Built to cross one of the steepest valleys along the Douro River, the Ponte Maria Pia was the first major work to emerge from the French firm of Gustav Eiffel  and Company, establishing Eiffel as an important bridge designer and civil engineer of his day. Resting on a parabolic arch spanning 160 meters, the Ponte Maria Pia was the longest iron arch bridge in the world at the time of its construction. The bridge's latticework construction reflects the later design of the well-known Eiffel Tower, erected in Paris to commemorate the International Exposition of 1900. 

The crossing of the Delaware River at Easton, Pennsylvania, provided a central link in travel from the northeastern seaboard to America's inland territories throughout the 18th and early 19th centuries. From 1806 to the mid-1890s, travelers used a landmark wooden structure built by noted bridge-builder Timothy Palmer. By the 1880s, however, Palmer's three-span covered bridge could no longer handle the demands of traffic generated by new trolley lines.

In the 1850s, the Lexington and Danville Railroad began building a suspension bridge over the Kentucky River. The bridge was designed by John A Roebling. Due to unforeseen increases in train loads, the Roebling bridge was never completed. The High Bridge would then be built 20 years later on the existing foundations.