 Horne was born in New York City, New York on February 14, 1880 to George Edward Horne and the former Marguerite Agnes Cooper.He was appointed from the state of New York to the United States Naval Academy at Annapolis, Maryland, on May 20, 1895.As a naval cadet, he served in the Spanish–American War aboard the gunboat and the battleship during the summer of 1898; he participated in the Battle of Santiago de Cuba on July 3, 1898.