Three of the ships were built by Bethlehem Shipbuilding Corporation, Quincy, Massachusetts with Quirigua being the second, preceded by Antigua and followed by Veragua.

The other three, built by Newport News Shipbuilding, were Chiriqui, Peten (originally Segovia, later Jamaica) and, the first of the six to be launched, Talamanca.

Construction in U.S. yards was a result of the Merchant Marine Act and more liberal government support in the form of mail contracts.

[6] The carriage of fruit was the primary purpose of the ships, though passengers, mail and general cargo were important components.

Propulsion was by two 3,150 volt, 4,200 kilowatt, 5,500 horsepower at 125 revolutions GE electric motors driving twin 15 ft 6 in (4.7 m), 3 blade screws.

[1] The planned crew breakdown by department was deck 24, engineering 34, stewards (passenger services) 48, and doctors, pursers and radio operators 6.

Some hold space became ammunition storage and naval alarm and electrical systems, including degaussing, were added.

[21] For the next year Mizar operated in the western Atlantic from a number of US East Coast ports supplying bases and ships from Iceland to the Virgin Islands.

[17] Mizar was then modified with more berthing before departing from Norfolk, Virginia, 10 June 1942 with task force TF 39, carrying the 1st Parachute Battalion attached to the 1st US Marine Division who were to take part in the invasion of the Solomon Islands.

[17] The Army forces engaged in the New Guinea campaign were suffering a critical shortage of fresh food requiring refrigerated transport.

In August 1943 the Navy made unused refrigerated space in Mizar available on trips into Milne Bay, New Guinea to help meet Army requirements giving some relief as the Army sought more refrigerated space in its own vessels assigned to the South West Pacific Area.

[23] Mizar made seven unescorted voyages to San Francisco, California, between 12 October 1942 and 9 February 1945 to get fresh meat, fruit, vegetables, dairy products and eggs to supply advanced bases and combatant ships.

[17] After the advance of US and Allied Forces in the Pacific she extended her Australian-based service to the Admiralty Islands in May 1944 and anchored in Leyte Gulf in the Philippines on 18 February 1945.

[17] Mizar reached San Francisco 25 January 1946 making her last Pacific crossing but soon received orders to go to the US East Coast.

Previewing a return to civilian status, en route she took bananas for the United Fruit Company from Quepos, Costa Rica to Charleston, South Carolina.

[17] Mizar averaged over 5,000 miles a month in World War II and received four battle stars for her service.

[16] In August 1946, still in its wartime configuration, paint and with the F-12 on its bow, the ship entered Bethlehem Steel's Staten Island Shipyard at Mariners Harbor for conversion to its former role and name.

[15] In 1958 United Fruit transferred Quirigua and her sisters Talamanca and Veragua to its British subsidiary Elders and Fyffes.

The five that the Navy obtained under bareboat charter through the War Shipping Administration and commissioned in effect formed a class.