Diamond State was laid down on 22 November 1960, as the break-bulk freighter SS Japan Mail, ON 287976, IMO 5170185, a Maritime Administration type (C4-S-1s) hull, under MARAD contract (MA 87).

In 1971 she was lengthened and converted to a type (C6-S-1a) hull container ship by Bethlehem Steel, San Francisco, California.

In 1988 the ship was converted to a type (C6-S-1aq) crane ship, completed 15 December 1988,[1] and assigned to the Ready Reserve Force, (RRF), under operation control of Military Sealift Command (MSC) and placed in service as SS Diamond State (ACS-7), 22 February 1989.

and assigned to Maritime Prepositioning Ship Squadron Three and was maintained in a five-day readiness status (ROS 5).

She was removed from MSC control, withdrawn from the RRF by reassignment to the NDRF (Beaumont, Texas) on 28 July 2006.