Betelgeuse was laid down as a C-2D on 9 March 1939 at Chester, Pennsylvania, by the Sun Shipbuilding & Drydock Co., Hull 180 under a Maritime Commission contract (MC hull 31); launched as Mormaclark on 18 September 1939; sponsored by Miss Anne Perry Woodward; delivered to the Moore McCormack Lines, Inc., on 29 November 1939; acquired by the Navy on 29 May 1941; renamed Betelgeuse on 3 June 1941; converted for naval service by the Brewer Dry Dock Company, Staten Island, N.Y.; and commissioned as AK-28 on 14 June.

Returning to New York on 25 March, she took on more supplies and sailed on 8 April with a convoy bound for the Tonga Islands, where the Navy was setting up an advanced base to consolidate the defenses of the communication and logistics lines with Australia.

Leaving Hawaii on 31 July and arriving in "Ironbottom Sound" off Guadalcanal on 7 August, Betelgeuse quickly unloaded her cargo in the face of Japanese air attacks.

For the next five months, the cargo ship made resupply and reinforcement voyages to Guadalcanal and Tulagi in support of the campaign to overcome the stubborn Japanese resistance there.

Reclassified an attack cargo ship, AKA-11, on 1 February, Betelgeuse sailed for the east coast and arrived at Charleston, South Carolina, on 8 March for the alterations that would fit her for her new role.

After preinvasion training off Salerno in June and early July, the "Camel" force, of which Betelgeuse was part, formed up at Palermo and set out for the southern coast of France.

The ship then made five more trips from ports in North Africa to points along the French and Italian coasts carrying equipment and troops to feed the Allied advances.

On 9 April, Betelgeuse departed Okinawa and headed for Port Chicago, California, whence she made two shuttle runs carrying ammunition to Pearl Harbor before the war ended.

Arriving at Tientsin on 10 November, she received orders that sent her to Guam, Pearl Harbor, and San Francisco to carry returning soldiers home in time for Christmas.

Refitted for merchant service, she operated as Mormaclark until sold on 27 June 1947 to Compania de La Paloma, S.A., out of Ancon, Canal Zone, under the name Star Betelgeuse.