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.

Civil War, the corps consisted of a total of one hundred and five commissioned officers and seven hundred and fifty-two enlisted men.

The duties required of the corps during the war were multitudinous, but consisted principally in planning, tracing, and superintending the construction of all fortifications, of whatever nature, needed in military operations, whether these works were of a temporary or a permanent character; and also in planning, laying-out, and constructing all works needed for the attack or the defense of fortifications. The corps was charged with the duty of securing and reporting upon the topographical features of the country through which the armies were operating, to the extent of furnishing maps and detailed descriptions sufficiently clear and accurate to permit the commanding generals to order the movement of troops with certainty as to the ground over which these troops were to maneuver.

On the field of battle, the exact knowledge of the terrain often decided the result, and the advantage was with the officers who had the best maps. On both sides these were furnished by the engineer officers. They were frequently charged with the duties of selecting positions for camps, either fortified or otherwise, and of reconnoitering the positions of the foe. They had charge of the bridge-equipage of the armies, and under their supervision were built the great structures used for the passage of immense bodies of men over the rivers of the South. Engineer troops were instructed in the arts of sapping, mining, building pontoon bridges, and quickly constructing “hasty entrenchments.” Engineer officers not on duty with troops were utilized on the staffs of the commanding generals.

At the outbreak of the war, there were practically no engineer troops — only one small company, which had been organized during the Mexican War. By the act of Congress of August 3, 1861, already referred to, a battalion of four