Sycamore was launched by the DUBUQUE BOAT AND BOILER WORKS on June 16, 1941 and was commissioned on September 9, 1941. She was assigned to the 9th District and was initially stationed at Dubuque where she was responsible for maintaining aids to navigation on the upper Mississippi River with short runs on the Minnesota and St. Croix Rivers. While on the upper Mississippi River she was involved in a search for a B-25 Mitchell bomber that had crashed in Lake Pepin. After 24 hours, she located the bomber during dragging operations. The aircraft was successfully salvaged. The Sycamore was transferred to La Crosse, Wisconsin beginning on April 1, 1942 and returned to Dubuque on March 1, 1944.
On February 26, 1952 the Sycamore was transferred to Cincinnati, Ohio, where she remained based until January 7, 1958. Here she was responsible for maintaining aids to navigation on the Ohio River from Ravenswood, West Virginia at the upper end, to Louisville, Kentucky at the lower end. On January 8, 1958 she was transferred to New Richmond, Ohio. Here she was responsible for maintaining more than 277 aids to navigation over 325 miles of the Ohio River. On February 8, 1964 she returned to Cincinnati until January of 1966 when she transferred to Memphis, Tennessee where she was responsible for tending aids to navigation along 130 miles of river, from Curuthersville, Missouri to the Memphis Highway Bridge.
On October 25, 1968, while assisting two vessels that collided, the M/V Pat Chotin and the M/V Hugh Blaske, Sycamore encountered two burning barges floating downstream, one loaded with 29,000 barrels of gasoline and diesel fuel and the other filled with grain. With raging fires blazing from the fuel barge and fuel spilling overboard, Sycamore's crew fought the fires, forced the barge aground and skillfully maneuvered it away from the smoldering grain. She and her crew were awarded the Coast Guard Unit Commendation Ribbon.
During 1970, she placed more than 4,400 buoys on station and moved or established her 95 shore towers 137 times. During a single trip during the summer of 1969 her crew set 400 buoys, built eight towers, and cut brush from around 12 others. While stationed in Memphis, she assisted in fighting a fire on board the M/V Ouachita 24 miles south of Memphis. On June 19, 1973 she transferred to Sewickley, Pennsylvania. Here she tended 225 buoy stations over 447 miles of waterway, including the Ohio, Monogahela, and Allegheny Rivers between Point Pleasant, West Virginia to Pittsburgh, Pennsylvania, Pittsburgh to Fairmont, West Virginia, and Pittsburgh to Greensboro, Pennsylvania.
During her Coast Guard career, Sycamore was awarded two Coast Guard Unit Commendation Ribbons. She was decommissioned on June 30, 1977.