[1] Duane graduated from Union College in 1844, where he was a founding member of Chi Psi fraternity,[2] and from the United States Military Academy in 1848, where he ranked third in his class.

Serving with the Army's company of sappers, miners, and pontoniers for nine years before the American Civil War, he led the engineers on a 1,100-mile march on the Utah Expedition in 1858 and commanded select engineer troops to guard President Abraham Lincoln at his inauguration in 1861.

Duane built the first military pontoon bridge over the Potomac River at the Battle of Harpers Ferry in 1862, served as Chief Engineer of the Army of the Potomac from 1863 to 1865, and in seven hours in 1864 built the longest pontoon bridge of the Civil War (2,170 ft) across the James River.

On April 10, 1866, President Andrew Johnson nominated Duane for appointment to the grade of brevet brigadier general in the Regular Army (United States), to rank from March 13, 1865, and the United States Senate confirmed the appointment on May 4, 1866.

[3] Duane commanded at Willets Point, New York, from 1866 to 1868, and for ten years constructed fortifications along the coasts of Maine and New Hampshire.