John Penn was named for John Penn, a Virginian who signed the Declaration of Independence. New York Shipbuilding launched her at Camden in 1931 as Excambion, a ship of American Export Lines. The Navy acquired her on 8 January 1942. Captain Harry W. Need took her when she was commissioned on 6 April 1942. She had come in as AP-51. On 1 February 1943 she was reclassified APA-23.
Fitting out and training led into the invasion of North Africa. Loading occupied 4 October through 16 October 1942: Army equipment, cargo, troops, and a last fill of fuel. On 23 October she left Hampton Roads in company with the Western Naval Task Force under Admiral Hewitt. Her group was the Northern Attack Group, Rear Admiral Monroe Kelly. On 8 November she lay off Mehdia, in western Morocco, and started troops and cargo ashore. Heavy surf and enemy shore batteries hindered the work. She still got the load off. At 1053 an enemy plane attacked, and the after guns shot it down. She shifted to Casablanca on 15 November, arrived that day, and finished the cargo. On 17 November she sailed for Norfolk and arrived on the 30th.
On 17 December she departed Norfolk for the Pacific and, by way of the Canal Zone, reached New Caledonia on 18 January 1943. She sailed on 24 January, called at Espiritu Santo three days later, and went to bring off survivors of the cruiser Chicago (CA-29), which had gone down on 29 January off Guadalcanal. She took aboard 1,003 men and 63 officers. Captain R. C. Davis, who had commanded the cruiser, was one of them. They left her at Noumea. Through the half year that followed, supplies, equipment, and troops kept moving. Guadalcanal was where they went. She loaded them in the New Hebrides, in the Fiji Islands, and in New Zealand.
On 13 August she was off Lunga Point and had just put 155-mm ammunition ashore when torpedo planes attacked at 2120. Three minutes later she took one plane under fire. It flamed and struck her mainmast. At about that same instant a torpedo from another plane hit. The people aboard tried to save her. At 2150 she sank by the stern. Her crew was reassigned, and those men served in later battles. One battle star was awarded.