Coast Guard Group Portland comprises small boat stations and several tenant commands that base themselves within the Group's area of responsibility (AOR). The AOR comprises a portion of the state of Maine, and all of New Hampshire. From the North, at Port Clyde, Maine, the AOR extends southward to the NH/MA border (just south of Hampton Harbor, NH), and includes offshore waters.
The land presently occupied by Coast Guard Group Portland was acquired in 1929 by the USLS for use as a depot. A channel 16 feet deep and 100 feet wide was dredged into the facility through mud flats from the natural deep-water channel of the Fore River in the north side of the Harbor. Of the 7.1 acres of land that presently exists within the facilities property bounds, nearly 50% was created in the early 1930s using approximately 124,000 cubic yards of material produced during dredging of the channel and a 300 foot turning basin just to the north of the facility. Overlapping sheet metal pilings were driven into the mud and then the dredged material was used to fill in behind. After allowing this area to settle for about one year, it was topped with hard fill trucked in from off base.
By the mid-1930's, construction of Building 1, 2, 3, and 4, the wharf and two piers (75 by 250 feet each) had been completed. In 1942, a temporary wooden barracks building was added on the upper-facility grounds. A Navy Net Depot was established in December 1941 with a large enlisted barracks, warehouse and workshop across High Street from the facility on 2.27 acres. The Navy depot existed as a tenant command of the Base until 1946. In that year, the annex was transferred to the Coast Guard. The Coast Guard used the buildings for several years until the U.S. Government declared them excess. The land and buildings were sold in July 1964 for $12,505.50. The wooden barracks building on facility was raised in 1963 and a new barracks and messing building (Building 6) was constructed in 1964 and a Boat Maintenance Facility (Building 7); Finger Pier and Travel Lift were added in 1982.
When the USLS merged with the Coast Guard in 1939 existing facilities were converted from a USLS Buoy Depot and Headquarters to a Coast Guard base. By the end of World War II, Base South Portland had become a home for all Portland Captain of the Port (COTP) and Portland Group activities with the Commanding Officer of the Base acting as COTP and Commander, Group Portland. This postwar Group was a consolidation of five wartime groups.
In 1952, the Group Portland offices were moved to Cape Elizabeth Lifeboat Station and Base South Portland commenced operation as an independent District unit. In 1960, the Group offices were moved back to the Base as a tenant command. In 1966, a major Group reorganization throughout the First District established a Captain's (O-6) billet at South Portland to perform a triple function as Commander, Group Portland; Commanding Officer, Base South Portland; and COTP Portland. The Marine Inspection Office located in Portland's Federal Building became Marine Safety Office in 1976. At that time, the MSO Commanding Officer assumed the responsibilities of COTP. The MSO offices were moved to the newly renovated U.S. Customs House in 1984.
A second major organizational reorganization of the Coast Guard took place between 1995-1996. At that time Base South Portland was disestablished as a separate command and all Coast Guard Reserve Commands were decommissioned and integrated into the Active Command structure. The functions of the industrial support facility and electronics support were transferred to the Integrated Support Command in Boston under the purview of the Maintenance and Logistics Command Atlantic. However, three independent units were created known as the Industrial Support Detachment Portland (ISD South Portland), the Electronics Support Detachment South Portland (ESD Portland), and the Maintenance Assist Team South Portland (MAT Portland). These three commands became tenant commands at the Group Portland Facility.
Portland has been the homeport for many major Coast Guard cutters (i.e. 200 feet or larger), but over the last decade, the number of these larger vessels based here has slowly decreased until, in 1985, USCGC Duane, the last of the major cutters in Portland, was decommissioned. The USCGC Spar was homeported at the Group Portland facility until it's decommissioning in 1997. The 175 foot buoytender the USCGC Marcus Hanna has been homeported at the Group Portland facility since it's commissioning in 1997.