The Liberty ship was completed on 14 August 1945, and chartered under general agency agreement by Waterman Steamship Co. until 17 June 1946, when she went into the Maritime Reserve Fleet.

Until they were decommissioned in December, 1969, these ships continued to act in that capacity, supplementing land based radio-intelligence monitoring of North and South Vietnamese and Cambodian VHF and HF communication nets.

Jamestown was redesignated AGTR-3 on 1 April and 8 days later departed on her first deployment visiting Gibraltar; Valletta, Malta; Aden; Cape Town; and Freetown, Sierra Leone, before returning Norfolk 17 August.

She stood out of Norfolk 2 November for Dakar, Senegal, Cape Town, South Africa, and further service acquiring new knowledge in the vital field of electronic communications.

After operation in the Caribbean in the spring, she transited the Panama Canal for a cruise along the Pacific Coast of South America reaching Valparaíso, Chile, 9 June.

The citation reads (in part): "For meritorious service from 1 November 1965 to 30 June 1969 while participating in combat support operations in Southeast Asia.