USS Libra, a 10,713-ton Arcturus class cargo ship, was built as the merchant ship Jean Lykes at Kearny, New Jersey. She was acquired by the Navy in late December 1941, while still fitting out, and was placed in commission in mid-May 1942. Libra soon sailed for the south Pacific, where she participated in the invasion of Guadalcanal and Tulagi in early August. During the next three months, she transported equipment and supplies among the bases supporting the campaign to hold Guadalcanal. In November, she helped to fight off Japanese air attacks on shipping off Guadalcanal, and made several more voyages into the battle area during the rest of 1942 and in the early part of 1943.

Reclassified as an attack cargo ship in February 1943, with the new hull number AKA-12, Libra continued to support operations in the Solomon Islands for the rest of that year, including participation in the Rendova landings in late June and the Bougainville invasion in November. In 1944 and 1945, she carried cargo throughout the southern and western Pacific, and was part of the amphibious forces that assaulted Guam in July 1944, Lingayen Gulf in January 1945 and Iwo Jima a month later. After the fighting ended in August 1945 Libra took part in the occupation of Japan.

Libra kept busy with Pacific Fleet logistics duties until late 1947, when she was sent to Boston, Massachusetts, for inactivation. Decommissioned in April 1948, she was in "mothballs" for somewhat more that two years. The Korean War crisis produced a recall to active duty, and Libra was recommissioned in August 1950. For the first half of the decade, she served with the Atlantic Fleet Amphibious Force, deploying to the Mediterranean Sea in 1954 and frequently operating in the Caribbean. USS Libra was laid up for the last time in October 1955. She was transferred to the Maritime Administration in July 1964, and remained in the National Defense Reserve Fleet for many years after that.