1779
On March 11, 1779, Congress establishes the U.S. Army Corps of Engineers to help plan, design and prepare environmental and structural facilities for the U.S. Army. Made up of civilian workers, members of the Continental Army and French officers, the U.S. Army Corps of Engineers played an essential role in the critical Revolutionary War battles at Bunker Hill, Saratoga and Yorktown.
The members of the Corps who had joined at the time of its founding in 1779 left the army with their fellow veterans at the end of the War for Independence. In 1794, Congress created a Corps of Artillerists and Engineers to serve the same purpose under the new federal government. The Corps of Engineers itself was reestablished as an enduring division of the federal government in 1802.
Upon its reestablishment, the Corps began its chief task of creating and maintaining military fortifications. These responsibilities increased in urgency as the new United States prepared for a second war with Britain in the years before 1812. The Corps’ greatest contribution during this era was to the defense of New York Harbor—the fortifications it built not only persuaded British naval commanders to stay away from the city during the War of 1812, but later served as the foundations for the Statue of Liberty.
moar: https://www.history.com/this-day-in-history/congress-establishes-the-u-s-army-corps-of-engineers