By the mid-19th Century, silt was quickly filling dredged shipping channels in the Mississippi's delta as the river flow began to slow and spread out. Navigation was further hindered by a sandbar in the Gulf of Mexico just off the river mouth that reduced water depth to just 8 ft. Large merchant ships were denied access to New Orleans and ports upstream except in high-water months. One solution that began to draw widespread enthusiasm was construction of a $13-million, 7-mile-long ship canal 75 miles below New Orleans from Fort St. Philip to Breton Sound.

Eads had a different idea, believing he could create permanent deep-draft navigation channels in the river at a cost far less than the canal. He proposed to Congress to build and maintain for 10 years a channel 28 ft deep and 350 ft wide through the Mississippi's Southwest Pass and out through the bar.

Eads even offered to finance the project until his channel was 20 ft deep. Then, he would be paid $1 million and receive further $1-million payments for each subsequent foot of depth until the channel reached 28 ft. Eads would then receive $500,000 each year for 10 years on condition that the channel maintained its depth.

Eads' plan was not universally embraced. The Army Corps of Engineers, which considered river regulation its exclusive domain, fought his proposal. In the end, Eads was forced to accept a deal in which he would provide a 30-ft channel and maintain it for 20 years. The project had to be located in the smaller, less workable South Pass and would generate $3 million less revenue than he proposed.

Undaunted, Eads went to work in 1875. By narrowing the South Pass, he increased the speed of the river flow to flush sediment out of the channel and carry it out into the Gulf. Eads built jetties along the pass, using willow brush mattresses as his main material. These were pine frames about 100 ft long and 18 in., deep crammed with brush. They were towed into place and sunk with rubble. Sediment quickly filled the space between branches. Eventually mattresses were piled on top of each other and held down by huge concrete blocks when they reached the proper height.

After eight months of work, the 8-ft channel at the bar had been deepened to 13 ft. By August 1876, Eads achieved a 20-ft-deep opening. Three years later, the channel had reached the 30-ft-deep mark and the force of the constricted Mississippi had entirely removed the bar at the head of the South Pass.

Infrastructure Booms in 1870s

In the late 1870s, construction was booming across the U.S. Bridges, dams and other infrastructure set new records and introduced equipment and approaches that revolutionized the industry. But progress did not come easily.

In 1879, the nation's first entirely steel bridge was built. Designed by William Sooy Smith, the Chicago and Alton Railroad Bridge over the Missouri River at Glasgow, Mo., was made up of five 314-ft-long Whipple trusses. During erection of one of the trusses, falsework failed and fell into the river. Although many members were bent, none broke. However, increased weight of rail traffic forced the bridge's replacement 20 years later. Also that year, Lester A. Pelton invented and patented the Pelton impulse waterwheel. His efficient system eventually stimulated development of hydroelectric power generation throughout the world.

The Hudson-Manhattan Railroad Tunnel under the Hudson River was also begun in 1879. Excavation was done using compressed air, but a blowout killed 20 workers. Tunneling difficulties and financing problems delayed the project's completion until 1904. And, after the 1879 collapse of Scotland's Firth of Tay Bridge, wind forces emerged as a new consideration in bridge design. Winds of 80 mph blew 13 of the bridge's truss spans--each 200 ft long--from their high piers. The collapse killed 75.

Other precedent-setting spans of the era fared better. The High Bridge, a Cincinnati Southern Railway span across a 200-ft-deep Kentucky River gorge at Dixville, Ky., was successfully completed in 1877. It became the world's highest and longest cantilever. Designed by Charles Shaler Smith and L.F.G. Bouscaron, the superstructure was 1,125 ft long. At the same time, Ernest L. Ransome was building the Alvord Lake Bridge, the first reinforced concrete arch bridge, in San Francisco's Golden Gate Park.

New tools and processes also expedited work. Wheeled scrapers, built by an Iowa contractor for work on a Burlington Railroad spur, were a big improvement over slip scrapers then used in railroad construction. The Vulcan single-action steam pile hammer was introduced in 1875, allowing faster pile driving with lighter rigs. Also that year, the first demonstrated use of rapid sand filtration in a municipal water system occurred in Louisville, Ky. In Allegheny County, Pa., builders of the Davis Island Lock and Dam on the Ohio River introduced the country's first rolling-lock gate, making the structure the largest movable dam built in the 19th Century. Building construction technology was also furthered by the 1876 completion of the William Ward House in Port Chester, N. Y., the first reinforced concrete building in the U. S.