William Arthur Mellon [also known as W. A. Mellon] was born in Melbourne, Victoria, Australia on 22 February 1871. By the early 1900s he had moved to England and was active as an architect in Workington, Cumberland [now Cumbria], England. In 1904 he submitted an unsuccessful entry in a competition to design the the Mitchell Library in Glasgow. His designs are illustrated in British Competitions in Architecture vol. 1, no. 5, September 1905 (p. 40). Prior to this, in collaboration with George Wittet of York, he had won a competition to design the Public Library and adjoining Carnegie Lecture Hall in Workington in 1904.
Mellon's address was given as 26 Washington Street, Workington, Cumberland in 1905. By 1911 he had moved to London. His is address was given as 66 Stand on the Green, Chiswick, London in 1911 and 19 Manor Court, Streatham, Lambeth, London in 1939. He died in Surrey, England in 1942