Lewis Hancock was born on October 15, 1889, in Austin, Texas. He entered the U.S. Naval Academy in June 1906, and graduated in June 1910. After serving aboard the battleship USS Vermont (BB-20) for two years, he was commissioned an Ensign in March 1912. After completing submarine training, Hancock served aboard the submarine USS G-1 (SS-19) from 1912 to 1913, and then commanded the submarine USS C-2 (SS-13) from 1913 to 1915. His next assignment was as commander of the submarine USS L-4 (SS-43) from her launching in April 1915, through her commissioning in May 1916, and during combat operations in World War I from 1917 to 1918. LT Hancock next commanded the submarine USS L-7 (SS-46) at the end of World War I, followed by service aboard the battleships USS Georgia (BB-15) and USS Wyoming (BB-32). After commanding the destroyer USS Sloat (DD-316), LCDR Hancock served on shore duty with the Navy Department and Department of Commerce in Washington, D.C., before being assigned to airship duty in 1922. He was designated a Naval Aviator in 1924 while serving aboard the airship USS Shenandoah (ZR-1), and was killed when the Shenandoah crashed in Ava, Ohio, on September 3, 1925. He was serving as the airship's Executive Officer at the time of his death. The destroyer USS Lewis Hancock (DD-675) was named in his honor in 1943.

His Navy Cross Citation reads:

The President of the United States of America takes pleasure in presenting the Navy Cross to Lieutenant Commander Lewis Hancock, Jr., United States Navy, for distinguished service in the line of his profession in Command of the L-4 during World War I. Under his command this vessel made numerous contacts with the enemy, and on one occasion attempted the dangerous feat of diving at a submerged enemy submarine to ram her.