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James B. Eads led the way back out of the abyss. A self-taught engineer who built ironclads for the Union Navy, Eads's experience with iron taught him the defects of the metal. When he began after the war to push his scheme for bridging the Mississippi at St. Louis, he conceived the notion of a great triple arch of steel. In those days, steel was an untried structural metal that cost three times what it does today. But Eads knew it also had twice the strength of wrought iron and could be worked in a way that iron never could. It took Eads more than seven years and $7,000,000, but what he built was a magnificent, 1,524-ft. bridge that was also one of the world's first important steel constructions of any kind. Scientific American was so impressed that it proposed Eads for President.
Cable. While Eads was working with rigid steel, other innovators were developing the concept of the suspension bridge—a primitive invention never much fancied by later bridge builders because of its nasty tendency to dump travelers or blow down. But with the invention of steel cables, the principle of bearing the load from above took on new fascination. As it turned out, suspension bridges were found to be the sole reasonable way of bridging long spans, since only suspension bridges can economically support dead weight beyond 1,600 ft.
Early experiments were shaky; in 1850 a regiment of French soldiers fell to their death from a suspension bridge at Angers. But a year later, German-born John Roebling began assembling a suspension bridge—over, of all places, the Niagara gorge and to carry, of all things, a railroad.
Wind. It took Roebling four years to build the 821-ft. Niagara bridge, but beginning in March of 1855, trains began regular crossings over a span held up by wire cables for the first time in history. Twelve years later he began planning his greatest work, the Brooklyn Bridge. Surveying the East River for the location of the main piers, he had his foot crushed. The injury gave him tetanus, and he died three weeks later. The man who took over the job was another Roebling—his son, Washington, who saw the bridge to completion in 1883. At a cost of $15 million and 20 lives, the Brooklyn Bridge set a record length of 1,595 ft. and set builders striving for even greater spans. In 1931, Builder Othmar Ammann spun the George Washington Bridge 3,500 ft. across the Hudson River; in 1937, Cincinnati Engineer Joseph Strauss carried the Golden Gate 4,200 ft. across the entrance to San Francisco Bay.