- Historic Sites
Mr. Eads Spans The Mississippi
The odds were all against him. His only credential seemed to be self-confidence—and who had ever heard of a steel bridge?
August 1969 | Volume 20, Issue 5
The St. Louis (later renamed the Baron De Kalb ) was followed by six others, including the conversion of Submarine No. 7 into the Benton . Because he had not quite succeeded in meeting the unrealistic deadline specified in the contract, the War Department bureaucratically delayed payment, so that the gunboats still technically belonged to Eads when Flag Officer Andrew H. Foote employed them to capture Fort Henry and support Grant at Fort Donelson. Subsequently these and other Fads-built ironclads distinguished themselves at Island No. 10, Vicksburg, and Memphis, where they became the first ironclads ever to engage an enemy fleet. (See “The Carondelet Runs the Gantlet,” in the October, 1959, AMERICAN HERITAGE ). Preparing to assault Mobile Bay, Admiral David Farragut urged Washington, “Only give me the ironclads built by Mr. Eads, and I will find out how far Providence is with us.” Eads’s ironclads performed valiantly in the decisive naval victory that followed.
The end of the Civil War allowed Eads to focus his brilliant energies on what was to prove the crowning achievement of his amazing career: the bridge over the Mississippi at St. Louis. As already noted, the leaders of St. Louis, the center of the steamboat trade, had watched in dismay as Chicago, with direct rail connections to the East and the West, burgeoned into the transportation capital of the Midwest. What was clearly needed was a railroad bridge to replace the time-consuming practice of ferrying the railroad cars across the river from East St. Louis, Illinois. It there was anyone who could accomplish this and still protect the navigation rights of the steamboat operators, it was James B. Eads.
Most railroad bridges at that time were truss designs. The truss is a pattern of triangles, whose engineering value lies in the fact that they cannot be distorted by stress. The first truss bridges were built of timber, the most important pioneering being done by the Yankee covered-bridge builders of the early decades of the nineteenth century. Two or three of their designs were taken over wholesale for railroad bridges, and simply built in iron instead of wood.
But iron proved to be an unsatisfactory building’ material for railroad bridges. Cast iron, the cheaper form, had insufficient tensile strength. Wrought iron was better, but it was very expensive and also treacherous, owing to the difficulty of achieving uniformity in fabrication. When the Bessemer and Siemens-Martin processes were developed in Europe in the fifties and sixties, it became possible to use steel—heretofore a rare, almost exotic metal—for structural purposes. Although conservative engineers in Great Britain and the United States doubted that mass-produced steel could be made uniform, Eads enthusiastically adopted the new material.
He urged his fellow townsmen to build their bridge in steel, but in place of the universally accepted truss, he advocated a return to the old Roman bridge form of the arch. His design called for three giant arches, the center one 515 feet, slightly longer than the two side spans. These arches were to be mounted on four mighty foundations sunk to bedrock. Each arch would consist of four ribs, arranged in parallel pairs, rising underneath a double-deck roadway.
Each of the three arch spans was to consist of a series of steel tubes joined together. The orthodox way of erecting such arches would have been to build timber falsework, or scaffolding, in the river. But Eads knew he could not obstruct the daily river traffic. He proposed an ingenious solution: he would cantilever the arch ribs out from each foundation, supporting the steel mass with cables from above instead of with scaffolding from below.
This daring conception, full of untried features, was not warmly received by the engineering establishment. And though Eads’s prestige, persuasive talent, and powers of logic won wide acceptance for his plans, even his most loyal St. Louis backers thought it would be wise to have an experienced bridge builder as consulting engineer. When the contract for fabricating components for the superstructure was awarded to the Keystone Bridge Company of Pittsburgh, the nation’s leading bridge-building firm, J. H. Linville, the company’s president, was invited to examine the plans. Linville took one look and sent them back to St. Louis. “I cannot consent to imperil my reputation by appearing to encourage or approve of [the design’s] adoption,” he announced. “I deem it entirely unsafe and impracticable.” He thoughtfully enclosed a plan of his own, a more conventional iron truss, to be floated on pontoons and raised to position. But Eads, who had never seen the inside of an engineering school, had his own conclusions checked by two trained engineers, Colonel Henry Flad and Charles Pfeiffer. These two gentlemen not only approved the design but became devoted subordinates in the project, which Eads commenced at once. In August of 1867 a flotilla of pile drivers, work boats, derricks, engines, and barges gathered at the foot of Washington Avenue, the heart of the St. Louis waterfront.