Duncan was graduated from Dartmouth College in 1858. He was principal of the high school in Quincey, Mass. from 1858 to 1860, tutor at Dartmouth College from 1860 to 1862, and commissioner of schools in Grafton County from 1861 to 1862. In 1862 he became the major of the 14th Regiment of New Hampshire Volunteers, and in 1863 he was promoted colonel of the 4th Regiment of United States Volunteers. He commanded a brigade of black troops from Jan. 20 to Sept. 29, 1864. On Sept. 29 he was wounded at New Market Heights, Va. and was immediately brevetted a Brigadier General for meritorious conduct and gallantry. After the war he became a lawyer and served as an assistant commissioner of patents from 1870 to 1872.
From the description of Correspondence, ca. 1850-1866. (Dartmouth College Library). WorldCat record id: 237352450
