From 1873 through 1883 Poe served as engineering Aide-de-camp on the staff of William T. Sherman, who was then commanding general of the U.S. Army. In 1883 he was made Superintending Engineer of improvement of rivers and harbors on Lakes Superior and Huron, where he helped to develop the St. Marys Falls Canal. Many consider his crowning achievement to be the design and implementation of the first Poe Lock in the American Soo Locks in Sault Ste. Marie, as it was instrumental in making possible the shipping industry, including steel craft freighters, in the upper Great Lakes. Consequently, it was pivotal to the creation of the basic steel industry in the United States. Poe's creation was dismantled in the early 1960s with a larger, more modern lock being built on the same site. This new passageway was renamed the Poe Lock and serves the largest of the Great Lakes freighters to this day.