USS Obstructor (ACM-7) was a Chimo-class minelayer in the United States Navy during World War II. Built by the Marietta Manufacturing Company in Point Pleasant, West Virginia, as a U.S. Army mine planter, USAMP 1st Lt. William G. Sylvester (MP-5) was delivered in December 1942 to the U.S. Army Coast Artillery Corps, Mine Planter Service. She was named for the first coast artillery officer killed (at Hickam Field, Hawaii, on 7 December 1941) in action in World War II. The Sylvester's embarked crew was, in Army terminology, implemented in November 1942, designated the 12th Coast Artillery Mine Planter Battery stationed at Fort Miles, Delaware.