William Louis Marshall (June 11, 1846, in Washington, Kentucky – July 2, 1920) was an influential figure in the US Corps of Engineers. At age 16 Marshall enlisted in the 10th Kentucky Cavalry, Union Army. He graduated from the United States Military Academy in 1868 and was commissioned in the Corps of Engineers. Accompanying Lieutenant George Wheeler's Wheeler Survey expedition (1872–76), Marshall covered thousands of miles on foot and horseback and discovered Marshall Pass in central Colorado. He oversaw improvements on the Lower Mississippi River near Vicksburg and on the Fox–Wisconsin Waterway canal system in Wisconsin. As Chicago District Engineer from 1888 to 1899, he planned and began to build the Illinois and Mississippi Canal. Marshall made innovative use of concrete masonry and de