G. Horace Tarr (also Horace G. Tarr and Horace G. H. Tarr) was born about 1844 in Missouri. During the American Civil War, he enlisted with Company K. 20th Regiment, Connecticut Infantry Volunteers in September 1862, around the age 17. Following Chancellorville, he was promoted to Sergeant Major; following Gettysburg, he was promoted to 1st Lieutenant. He later served as Captain of Company F during the Atlanta campaign. He mustered out June 13, 1865. Following the war, Tarr worked as a engineer and manager for a series of businesses, including two iron companies (an industry in which his family was well established) and later, Otis Elevator Co., and several water utilities. By 1886, he was married with six children. Tarr died on March 2, 1922, at his home in Philadelphia. Although 78 years old at the time, he was still actively employed with the R. D. Wood & Co.

Tarr's name appears in 1863 and 1885 correspondence between Walt Whitman and his brother, Thomas Jefferson Whitman that suggests the Whitmans were on friendly terms with Tarr's uncle Moses Lane (1823-1882), and later Tarr himself.

Tarr died in 1922 and is buried with his wife Carolyn in Arlington National Cemetery, Arlington, Virginia.

Source: "Capt. Horace G. H. Tarr" entry, Findagrave.com, https://www.findagrave.com/memorial/49322668/horace-g_h-tarr.