Point in 1835 and spent just three months as an infantry lieutenant before resigning his commission to become a railroad surveyor. The next year he was an engineer of a line that ran from the Potomac to Gettysburg, Pennsylvania, a town that would figure in his life for a few busy days a quarter-century later and which also was the home of Ann Keller, who became his wife and bore him eleven children.

In 1840, at work on the York & Wrightsville, he grew suspicious of the design of the road’s latticework bridges and found to his astonishment that there was not a single engineer in the United States who had ever tried to calculate the strain of any even slightly complex bridge truss. He put a decade into the subject and produced his General Theory of Bridge Construction , which publishers at first shunned because they could find no engineer qualified to review it. But when the book finally appeared in 1851, it was an instant success and established its author as an authority in the field.

Haupt went on to serve as the Pennsylvania Railroad’s chief engineer before going north to Massachusetts in 1856 to take over the building of the Hoosac Tunnel near North Adams. This nightmarish project, which had begun in 1848 and would drag on until 1875, gave him a foretaste of the sort of frustration he would experience in the army. By the time the Civil War broke out, he was in litigation with the tunnel authorities, who refused to repay money he had spent to keep the work going after state funds had dried up. During what he called “this exciting contest,” he received an urgent summons from the War Department: Would he come serve as chief of construction and transportation on the United States military railroads? It was the worst possible time for Haupt to neglect his Massachusetts dispute, but he went.

His first job was to open up the Aquia Creek road out of Fredericksburg, a ravaged line whose bridges all were destroyed. The toughest problem was the wide Potomac Creek. Haupt had to bridge it with too few tools, wielded by some hundred soldiers who were deeply reluctant, he said, “to climb about on ropes and poles at an elevation of 80 feet.” But despite “scarcity of food and with several days of wet weather, the work was … advanced so rapidly that in nine days the bridge was crossed on foot.” The one it replaced had taken nine months to build.

Within two weeks Haupt was ready to test the finished span by pulling a locomotive across it with ropes: “If it goes into the creek,” he said, “it will cease to trouble us for a while. If it reaches the other side, it will have a good road.…” The engine passed over with majestic ease; soon the bridge was carrying twenty heavy trains daily. President Lincoln stopped by a few

days later and pronounced it the “most remarkable structure that human eyes ever rested upon. This man Haupt has built a bridge across Potomac Creek, about 400 feet long and nearly 100 high, over which loaded trains are running every hour, and, upon my word, gentlemen, there is nothing in it but beanpoles and cornstalks.”

Haupt hammered the Union roads into shape and somehow kept the trains rolling during the catastrophic second Bull Run. In September he was promoted to brigadier general of volunteers. As before, he refused to take any pay. When, early the next summer, Lee came north again, Haupt saw how things were shaping up, and he was in the right place and ready to move when the armies met at Gettysburg. The only line he could use was the wretched little Western Maryland, a twenty-nine-mile route bare of sidings, turntables, telegraphs, and water towers. It could handle four trains on a good day. Haupt needed to be able to run thirty. On July 2, with the battle in its second day, he had four hundred men of the Railroad Construction Corps splitting lumber and hauling water while he worked out the logistics of moving trains up and down a blind single track. By July 3, as Lee made his final thrust at the Union line, Haupt had all the problems licked and was shoveling fifteen hundred tons of supplies a day into the cauldron. By the time the battle ended, there was enough material on hand at the railhead to supply the victorious Union army for a week. Haupt hurried to the field and begged the Union commander, his old classmate George Gordon Meade, to pursue the retreating Lee. Meade refused; his troops were exhausted. To the end of his life, Haupt rankled under the conviction that the war could easily have been ended then and there.

Two months later the mounting pressure of his Hoosac Tunnel dispute forced him to leave the army. But by that time the Union had learned how to keep its trains running.

Haupt finally got his tunnel pay—to the tune of eight cents on the dollar—in 1884. By then he had been chief engineer of the Shenandoah Valley Railroad, general manager of the Richmond & Danville and the Northern Pacific, and the builder, over the Standard Oil Company’s vigorous opposition, of a pipeline that carried petroleum from the Allegheny valley to tidewater Maryland. He served as President of the Dakota & Great Southern and also found time to publish three more books, one of them a study of the coming form of transportation, Street Railway Motors .

He outlived every one of his West Point classmates and kept on working hard until December 14, 1905, when a heart attack killed him. He was aboard a train at the time.