Three names
Kaiser laid her down at Vancouver, Washington, on 23 January 1943 as Chapin Bay, Maritime Commission hull 1100. She was renamed Midway on 3 April 1943, launched on 17 August 1943, sponsored by Mrs. Howard Nixon Coulter, and commissioned on 23 October 1943. She was a Casablanca-class escort carrier: small, mass-produced, with a bow catapult, two elevators and a single 5-inch gun. On 10 October 1944 she was renamed St. Lo. The change freed the name Midway for a new large carrier and honored the Battle of Saint-Lô in Normandy, which had ended with the town's capture on 18 July 1944.
Ferry duty and the Marianas
As Midway she left Astoria on 13 November 1943 and made two ferry runs to Pearl Harbor and one to Australia with replacement aircraft. With Composite Squadron 65 (VC-65) aboard, she joined Rear Admiral Gerald F. Bogan's Carrier Support Group 1 in June 1944 for the Marianas. She covered the transports and struck Saipan, where her FM-2 Wildcats claimed four Japanese planes. After replenishing at Eniwetok she supported the Tinian landings from 23 to 28 July. On 13 September she sortied with Task Force 77 for the invasion of Morotai.
The Battle off Samar
At Leyte she sailed with Taffy 3 and struck the beaches near Tacloban. Early on 25 October 1944 she had just launched a four-plane antisubmarine patrol when Kurita's Center Force appeared. She and the other five carriers ran in and out of rain squalls and launched every fighter and torpedo plane they had, with whatever weapons were aboard. Her single 5-inch gun claimed three hits on a Tone-class cruiser. When Japanese destroyers fired a premature torpedo spread from 10,500 yards, the torpedoes were nearly spent by the time they reached the carriers. Lieutenant (jg) Tex Waldrop, flying a St. Lo Avenger, strafed two of them in Kalinin Bay's wake and exploded one.
At 10:50, after Kurita had turned away, the Shikishima Special Attack Unit struck Taffy 3. At 10:51 a Zero, perhaps flown by Lieutenant Yukio Seki himself, crashed onto St. Lo's flight deck. Seki may have been aiming for White Plains before flak turned him. The bomb went through the deck and burst on the port side of the hangar, where aircraft were being refueled and rearmed. Gasoline fires and secondary explosions followed, and her torpedo and bomb magazine blew up. She sank about 30 minutes later, the first major warship sunk by a kamikaze. Of the 889 men aboard, 113 were killed or missing and about 30 more died of wounds. Heermann, John C. Butler, Raymond and Dennis rescued the survivors, and Dennis alone picked up 434.
Honors and wreck
She received the Presidential Unit Citation with Taffy 3, four battle stars, and the Philippine Presidential Unit Citation. RV Petrel found her wreck on 14 May 2019 and surveyed it on 25 May. She sits upright in 4,736 meters of water on the edge of the Philippine Trench, near 11.02°N 126.04°E.
Sources
Wikipedia, "USS St. Lo" (citing DANFS; Hornfischer; RV Petrel survey).
NHHC/DANFS, "St. Lo."