About 18 miles below Fort Jackson at Head of Passes, the Mississippi River branches into Southwest Pass, South Pass, and Pass A Lutre before emptying into the Gulf of Mexico. As early as 1723, French colonists found navigation difficult and sought ways to deepen the passes. In 1875, Captain James B. Eads, a civil engineer, inventor, and shipbuilder from Saint Louis, proposed to Congress that jetties be built to deepen South Pass and that he would maintain a 30-foot channel for the next 20 years, with payment from the United States government only if he succeeded. On June 14, 1875, his crew began driving two lines of piles to extend the east and west banks of the pass as the outline for the jetties. Using willow mattresses stacked and weighted with stones called riprap, and later concrete slabs placed atop the jetties in December 1878, the work forced the river to scour a deeper channel that reached 26 feet by late December 1876 and 30 feet less than a month later. Eads maintained the channel for 20 years, and his maintenance contract expired in January 1901. The jetties revived the declining Port of New Orleans and helped the Mississippi Valley prosper: shipments from Saint Louis through New Orleans to Europe rose from 6,875 tons in 1875 to 453,681 tons in 1880. As commerce grew, jetties based on Eads' South Pass model were built at Southwest Pass between 1908 and 1928, and the largest ships bound for New Orleans began using its 35-foot channel. Ship traffic in South Pass was discontinued in the 1970s, and today Southwest Pass serves oceangoing vessels bound for ports between New Orleans and Baton Rouge, with the U.S. Army Corps of Engineers maintaining the channel to a 45-foot depth.