The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 5: Forts and Artillery.
Francis Trevelyan Miller, Ed.

[228] companies was provided for, and was assigned to the Army of the Potomac. It was utilized in constructing the defenses of the city of Washington in the winter of 1861-62, and during that time received instruction in the duties which it afterward performed so well in the field.

On February 24, 1862, the battalion was sent to Harper's Ferry, Virginia. There, under the greatest of difficulties, it constructed a pontoon bridge across the Potomac. The river was a raging torrent, the water being fifteen feet above the normal level, and filled with huge cakes of drifting ice and quantities of debris. It was with the utmost exertions that the pontoons could be pulled into position, and, once placed, they had to be secured with ships' anchors and chain-cables. But the structure was completed in about eight hours, and General Banks' corps, with all its trains and artillery, crossed safely and without delay. For a time the battalion was engaged in keeping the bridge in position and in good repair. General McClellan, himself an engineer of renown, stated in a letter to Secretary of War Stanton that it was one of the most difficult operations of the kind ever performed.

Immediately after returning to Washington from Harper's Ferry, the engineer troops, with their bridge-equipage, were sent to Fort Monroe, in Virginia, and were moved thence, on April 4th, to a Camp near Yorktown, in preparation for the Peninsula campaign. In front of Yorktown the battalion was engaged in constructing trenches and lines of communication, and in superintending and instructing details of soldiers who were unfamiliar with methods of modern warfare. At this period of the war (1862), the troops of the infantry and the cavalry had received no training in the construction of field-fortifications. Consequently, the duty fell heavily on this battalion of men who had received such instruction.

Orders to construct a bridge across the Chickahominy River were received late on the afternoon of the 31st of May. The river was rising rapidly, and the night was extremely dark.