Investigator (YAGR-9) was laid down on 28 November 1944, under a Maritime Commission (MARCOM) contract, MC hull 2336, as the Liberty Ship Charles A. Draper, by J.A.

[5] After a brief period of service in 1947, she entered the Reserve Fleet at Mobile, Alabama, until she was acquired by the US Navy, 2 July 1956.

[5][3] Equipped with the latest in air search and tracking systems, the ship conducted her shakedown training in the Caribbean, and departed Guantanamo Bay, for her new home port, Davisville, Rhode Island.

She continued radar picket station duties for CONAD, detecting and tracking inbound airborne objects and controlling jet interceptor aircraft until decommissioned 29 March 1965.

She was transferred the same day to the US Maritime Commission (MARCOM) and entered the Hudson River Reserve Fleet, Jones Point, New York, where she remained until sold for scrapping in Spain, 15 May 1971.