The son of Jane Renne and Charles F. Hammond, a prominent owner and operator of lumber and iron businesses in Crown Point, New York, John Hammond was born in Crown Point on August 17, 1827. He attended the public schools of Crown Point, Panton, Vermont, and St. Albans, Vermont, and graduated from the academy in St. Albans. He attended Rensselaer Polytechnic Institute and worked at his family's store in Crown Point before moving to California during the 1849 gold rush. He returned to Crown Point after several years in California, and resumed working in his family's businesses.