William Mullan was born in Garvagh, Co. Derry c.1815 and came to Belfast in 1830. He worked in the wholesale grocery business and was a close friend of John Lyttle, who had served as Mayor in the years before Mullan took office.

Mullan entered the Belfast Corporation in 1855 as councillor for St Anne’s Ward. He served in Council for twenty-six years. He was chairman of the Town Council cemetery committee and was a strong advocate of the construction of a cemetery on the Falls Road (now Belfast City Cemetery).

Mullan was a Harbour Commissioner for twenty years, having stood for election in a bid to strengthen the representation of interests other than ship-owing. As a member of the Methodist Church, Mullan was closely associated with the founding of Methodist College and acted as treasurer of the school’s building committee.

Mullan’s portrait was presented to his wife at the couple’s home in October 1874, with eighty of Belfast’s leading citizens and merchants in attendance.