Duportail was born near Orleans, France. After graduation from the prestigious military academy in Mézières, he joined the French government's program of covert aid to the American war effort. In 1777, he was appointed the Continental Army's chief of engineers. He began rebuilding forts on the Delaware River and organized the Valley Forge encampment. He fought at Monmouth and on the Hudson, and improved the defenses at Philadelphia and West Point.
In 1779, Duportail became commandant of the Corps of Engineers and Sappers (underground fortifications). He was captured during the siege of Charleston, and later fought at Yorktown. After a leave of absence in France, Duportail resumed his American command, not resigning until the end of the war in 1783. The French Revolution cut short his return to French military service. Duportail spent two years in hiding before returning to America. He settled near Philadelphia for a few years, but died in 1802 during a voyage back to France.