Tower was born at Cohasset, Massachusetts to a family settled at adjacent Hingham since its founding. He graduated with first honors at West Point in 1841. He served under General Scott in the Mexican War, led the storming column at Contreras, and was wounded at Chapultepec. After the war, Tower served as an engineer. He was responsible for the initial construction of the Federal facilities on Alcatraz Island in San Francisco Bay and Fort Point, San Francisco.