He was excellent at both building and destroying railroads . The use of railroads was new to warfare and he was a master at building and rebuilding them. He was the youngest cadet to ever graduate from West Point. That Man Haupt has built a bridge over Potomac Creek, about 400 feet long and nearly 100 feet high, over which loaded trains are running every hour, and upon my word gentlemen, there is nothing in it but beanpoles and cornstalks. When you need to move 400 wagons of baggage and supplies and 100,000 troops it makes Boston traffic look like a picnic in comparison.
Railroads make moving and supplying an army much more efficient.
General Meigs was also an engineer. During the war he would be the Quartermaster General of the Army. Although born in Georgia, his family moved to Philadelphia when he was young. His specialty was buildings. He was also involved with numerous other important projects including the Washington Aqueduct that supplied water to the nations capitol.