George A.C. Barnett was born in New Jersey c.1840, and enlisted in the Union army in New York City on April 23, 1861. He first served in the 9th Infantry, Co. B, then as adjutant for Co. G from May 29, 1863, to October 14, 1863. On December 29, 1863, he was promoted to 1st lieutenant. From October 1863 until March 1865, Barnett served in the 17th New York Veteran Volunteer Infantry as 1st lieutenant, Co. G, 1st lieutenant, Co. B, and as adjutant.
After the war, Barnett practiced law in Manhattan. New York City directories list him as lawyer from 1867-1874, a publisher from 1875-1878, and again as a lawyer from 1879-1881. Census records show that in 1870, Barnett was living in Morrisania, New York, with his wife, Emma. In 1910, he lived in Manhattan with his wife, daughter Pierce Edna, and grandson George. Barnett died in 1914.