During the US Civil War, George Grenville Barnum Jr. served as a captain in the 12th NY Volunteer Infantry. His service with that unit was from August 1862 to August 1865.
The town of Barnum, Minnesota was named for George G. Barnum, who was the paymaster of the Lake Superior Mississippi Railroad when it arrived in the village in August, 1870.
His DOB was 10/1/1843. He married in 1875. In 8/1876 he made a Homestead claim in Detroit, Minnesota (not Michigan). The 1880 US census shows that he and his wife had a daughter named Alice K. born about 1876. She does not appear in the 1885 census, suggesting her death by then. Their son, George G. Barnum III, was born in 1886. George G., Jr. and his wife traveled extensively around the world: passport applications have been found for 1906, 1911 and 1914. There are also passenger lists for ship voyages up to the age of 93 (identity confirmed by DOB and address in Duluth).