Green Mountain State was laid down on 2 December 1963 as the break-bulk freighter SS Mormacaltair, ON 298129, IMO 6421347, a Maritime Administration type (C4-S-60a) hull, under MARAD contract (MA 143).

US Lines ceased operations in 1986 and the ship was turned over to MARAD in 1987 and placed in the National Defense Reserve Fleet (NDRF).

The ship was converted to a MARAD hull type (C6-S-MA60d) Crane Ship at National Steel and Shipbuilding Co., San Diego, California, and placed in service as SS Green Mountain State (T-ACS-9) on 15 March 1992, assigned to the Ready Reserve Force (RRF), under operation control of Military Sealift Command (MSC).

[1] Green Mountain State was berthed at Bremerton, Washington, where she was maintained in a five-day readiness status, assigned to Maritime Prepositioning Ship Squadron Three.

She was removed from MSC control and withdrawn from the RRF by reassignment to the National Defense Reserve Fleet (Beaumont, Texas) on 28 July 2006.