Suncook was laid down at Portland, Oregon on 30 November 1944 by the Commercial Iron Works. The ship was launched on 16 February 1945, sponsored by Mrs. Laura B. Stephenson. Suncook was commissioned on 5 May 1945.
Suncook conducted shakedown and training off the California coast until 8 July, when she departed for Pearl Harbor. From there, she was routed on to Eniwetok Atoll in the central Pacific Ocean. She arrived at the anchorage on 1 August, just two weeks before the cessation of hostilities. There she tended nets for the next seven months, making one round-trip voyage to Ponape and back in December 1945.
In March 1946, she sailed to Guam in company with and after two weeks there, continued on to Bikini Atoll in the Marshall Islands, where she arrived on 30 March.
Suncook remained in the vicinity of Bikini and Kwajalein Atolls until September, supporting the atomic bomb tests known as Operation Crossroads. On 2 September, she cleared the area and sailed via Pearl Harbor to the U.S. West Coast. She reached Seattle, Washington, on 30 September and remained there until June of the following year, undergoing radiological clearance.
In January 1947, she was placed in reserve, but remained in commission. On 10 June, she departed Seattle, and arrived, two days later, in Astoria, Oregon, where she was placed out of commission. She remained with the "mothball" fleet until August 1961, when custody was transferred to the U.S. Maritime Administration.
In September 1962, she was again transferred, this time to the U.S. Bureau of Mines for use as a research ship at the Marine Mineral Technology Center at Tiburon, California.
Her name was struck from the Navy List on 1 September 1962 and she became the research vessel, Grass Valley. She served under that name until returned to the Navy for disposal on 18 June 1968. On 28 July 1971, her hulk was sold to the Waterman Supply Co., Wilmington, California.