The ship that would eventually be known as the USS Zeilin was constructed by the Newport News Shipbuilding and Drydock Company in Newport News Virginia as the Silver State under a U.S. Shipping Board contract. The Silver State was a member of the U.S. Shipping Board's 535-ft class, a combination passenger and cargo steamship with accommodations for 280 first class passengers and 194 third class.
'The SS Silver State operated between Seattle Washington and the Far East with the Admiral Orient Line a subsidiary of the Pacific Mail Steamship Company. On 23 June 1922 the SS Silver State was renamed the SS President Jackson when the ship was purchased by the Dollar Line owned by Robert Dollar. In 1938 the SS President Jackson was transferred to the American President Lines.
The SS President Jackson was acquired by the U.S. Navy in July 1940 and was renamed the Zeilinwith the designation AP-9 after Brigadier General Jacob Zeilin (July 16, 1806 - November 18, 1880) who was the first United States Marine Corps general.
After a shakedown cruise and training along the west coast of the United States, the Zeilin left San Diego on 13 April 1942 transporting troops to Samoa for garrison duty and returning to San Diego on 17 June 1942.
Early on the morning of 7 August 1942, Zeilin arrived off Guadalcanal with Task Force 62. On 8 August 1942 U.S. Marines from the 3d Defense Battalion were landed by Zeilinon Tulagi, Gavutu, and Tanambogo. After completing disembarkation of the U.S. Marines, the Zeilin traveled to Noumea, New Caledonia.
For the next two months, the Zeilintraveled a route between Noumea; Espiritu Santo New Hebrides, and Wellington New Zealand. On 9 October 1942, the Zeilindeparted Noumea to carry troops and supplies to the Solomon Islands.
Arriving off Guadalcanal on 11 October 1942, the Zeilin began unloading at Lunga Point. On 13 October 1942, the Zeilin was attacked by a Japanese shore battery; but the ship did not receive any damage. The Zeilin returned to Noumea on 17 October 1942 and then proceeded to Espiritu Santo before returning to Lunga Point on 11 November 1942.
At 09:00, the task group received a report that nine carrier bombers and 12 fighters were approaching from the northwest and would reach their vicinity at about 09:30. At about 09:20, USS Atlanta (CL-51) led the Zeilin and two other auxiliaries to the north, in column, with destroyers spaced in a circle around them. Fifteen minutes later, nine Japanese Aichi D3A "Val" dive bombers from the Japanese aircraft carrier Hiyō emerged from the clouds over Henderson Field.
At 09:40 the Zeilin opened fire. The Japanese airplanes dove on the Zeilin and released bombs at 1,200 feet. One aircraft was set on fire by the Zeilin's guns There were three near misses registered on the ship; two on the port side - one about amidships, the other aft; and one on the starboard side at about frame 45 opposite No. 8 hatch, depth about 15-30 feet. The ship suffered severely from this bomb.
The number 8 hold was flooded to the third deck; number 7 to the fourth deck. The starboard shaft was carried away. The Zeilin took on approximately 2,000 tons of water. Examination by diver later disclosed cracked and ruptured hull plating as the cause of the flooding.
Though damaged and listing, the Zeilin carried casualties to Espiritu Santo and then sailed via Tutuila, Samoa to San Pedro, California. The Zeilin arrived at the Terminal Island Naval Shipyard later known as the Long Beach Naval Shipyard on 22 December 1942 for repair. This repair work was completed in March 1943.
On 17 April 1943, the Zeilin left San Diego California for the Aleutian Islands. After a six-day stop in San Francisco California, the Zeilin continued on and arrived at Cold Bay, Alaska on 1 May 1943.
Cold Bay was the rendezvous point for the Attu Island invasion force. By 11 May, 1943 the Zeilin was located off the south coast of Attu Island, at Massacre Bay. After the initial landings, the Zeilin remained off Attu Island until 16 May, 1943.
The Zeilin traveled to Pearl Harbor Hawaii in mid September 1943. After a five day stay at Pearl Harbor Hawaii the Zeilin continued to Wellington New Zealand via Funafuti and Espiritu Santo arriving on 17 October 1943.
On 13 November 1943, the Zeilin departed Efate and arrived off Betio on 19 November 1943. Early the following morning, U.S. Marines from 2nd Battalion 2nd Marines were offloaded into landing craft from the Zeilin for their assault. During the unloading operation the Zeilin was under fire from Japanese shore guns. The ship did not sustain any damage from the attack.
For the next three months, the Zeilin carried troops and supplies for units operating in the Solomon Islands and in New Guinea. During this time period the Zeilin visited Guadalcanal and Bougainville in the Solomon Islands, Espiritu Santo, Milne Bay and Cape Sudest on New Guinea, and the newly conquered Admiralty Islands. On 10 May 1944, the Zeilin returned to Guadalcanal to prepare for the invasion of the Mariana Islands.
Leaving the Mariana Islands on 30 June 1944, the Zeilin arrived at the Eniwetok Atoll in the Marshall Islands on 3 July 1944. After 15 days, the Zeilin left Eniwetok Atoll and joined other transports carrying troops from Hawaii. The Zeilin arrived off Guam on 22 July, 1944 and unloaded the U.S. Marines over 4 days departing on 26 July 1944.
The Zeilin stopped overnight at Eniwetok Atoll again on 29 July 1944 before arriving at Pearl Harbor Hawaii on 7 August 1944. Then after 3 days at Pearl Harbor, the Zeilin departed for the west coast of the United States arriving at San Francisco California for a three month overhaul.
On 21 October 1944, the Zeilin departed San Francisco California arriving at Finschhafen on the west coast of New Guinea on 6 November 1944. The Zeilin visited Langemak Bay and Hollandia (now known as Jayapura) before arriving at Noumea on 22 November 1944.
The Zeilin loaded elements of the U.S. Army's 25th Infantry Division at Noumea and departed for Guadalcanal in the Solomon Islands in December 1944. At Guadalcanal, the task group including the Zeilin conducted training exercises. The task group left Guadalcanal on 25 December 1944 arriving at Manus in the Admiralty Islands on 29 December 1944.
The next morning, a single Japanese Kamikaze airplane attacked the convoy missing the amphibious command ship USS Mount Olympus (AGC-8) and striking the Zeilin. The right wing of the Japanese aircraft struck cargo loading equipment next to the number 6 cargo hatch. The fuselage of the airplane crashed into the starboard side of the housetop. Incendiary weapons carried by the aircraft exploded and started several fires on the ship. Topside damage to the Zeilin was extensive. The superstructure deck was destroyed, deck framing was damaged, and several staterooms were destroyed. The airplane's engine pierced the deck, the outboard bulkhead and landed in a landing craft carried by the Zeilin. Seven crew members were killed, three crew members were declared missing, and 30 crew members were injured. After the attack the Zeilin continued with the convoy and arrived at Leyte Island in the Philippine Islands. After receiving temporary repairs at Leyte, the Zeilin departed on 16 February 1945 arriving at Ulithi Atoll in the Caroline Islands on 18 February 1945.