Capt. William McLellan Sr. (ca. 1735-1815) was owner and master of the sloop "Centurian," one of the ships destroyed by the British during the Penobscot expedition in 1779. After the war, McLellan was a leading Portland merchant.

John Brewster, who painted the portrait, was born deaf. He trained as a painter and traveled the New England coast as an itinterant artist between 1796 and 1833.

He eventually settled in Buxton.