Sylvanus Backus (born 1839) was appointed an acting midshipman to the U.S. Naval Academy in 1857 from his home state of Michigan. After the Civil War began, he received an appointment as a lieutenant, and served on the Constellation, Ohio and Mohongo. He left the navy in 1866, and died about 1915.
His story, and this carte de visite by Hodcend & Degoix of Genes (Genoa, Italy), will be featured in my forthcoming book about the Civil War navies.