In the 18th century, Great Diamond Island was a private island owned by Deacon James Milk, who farmed and enjoyed the natural beauty of “Great Hogg Island,” followed by his heirs the Preble, Fessenden and Deering families. While the owners allowed Diamond Cove on the northerly end to be used for picnics and recreation, the island remained exclusively private until the US military purchased land on either side of Diamond Cove in 1873.


In 1882 an enterprising group of men from Portland, Maine, purchased from Henry Deering a large tract of land (approx. 245 acres) extending from Diamond Cove to the southwesterly segment of the island. It was their intention to establish a self-sufficient, planned community.  So they sold lots, established the Diamond Island Association, and changed the island’s name from Great Hogg (perhaps an indication of its former agricultural use) to Great Diamond Island, based partly on the ample supply of quartz crystals found on the island, but also surely to entice others to become property owners in the Diamond Island Association.  They had great plans for the island which included building their own wharf, the Casco Wharf; purchasing their own forty-five foot steam boat, the Isis; leasing the existing farm to furnish their own produce; establishing roads and areas for parks; setting up an acetylene gas production plant; erecting kerosene street lamps; establishing a water supply system; building a restaurant and meeting hall for association members; establishing a community store; and devising a set of by-laws which dictated how things would be.  A grand plan indeed!  

Today, approximately 100 acres of original Deering property at the southern end of the island remain privately owned, and about 200 acres at the northern end are also owned privately by Diamond Cove Homeowners’ Association. 


A more complete history of Great Diamond is available at The Store at Elwell Hall. There also are annual history exhibits at Elwell Hall and at the Museum at Diamond Cove.







Diamond Cove (DCHA), formerly historic Fort McKinley, covers approximately 193 acres on the northern end of Great Diamond Island. Fort McKinley was constructed by the US government between 1891 and 1907 and was designed to defend Portland Harbor during the Spanish American War. Originally Fort McKinley consisted of over 125 buildings surrounding a military parade ground and was home to over 1000 soldiers and their families. In 1945 the US Army declared Fort McKinley surplus and it sat vacant until 1961 when it was sold to a private developer. It was not until 1984, after much disrepair and public controversy, that restoration began by DicTar Associates and was finalized by McKinley Partners into the private resort community of Diamond Cove we see today. Restored Fort McKinley, representing an historic era of US and island history, is on the National Historic Registry and as such it remains open to the general public. Pedestrian access only is allowed and is restricted to Diamond Avenue and the Parade Ground. Viewing of the Gun Batteries and a narrated historic tour of Fort McKinley can be arranged by contacting tours@diamondcove.com.


No motorized vehicles, except those exempted by and on file with the City of Portland, are allowed in or out of private Diamond Cove property.