Urban Mayo was born in London, Ontario on 27 June 1918 to William and Emma Mayo. He had four brothers: Earl, William, Alan and Ernest, and two sisters: Myrtle and Ruby. Urban left school at age 16 after Grade 9 and, at the time of his enlistment, he had been working with Bennett and Wright as a plumber apprentice for four years. Urban supported his parents financially as his father was in his 80s at the time and partially blind while his mother was elderly and partially incapacitated. He enlisted on 30 May 1940 at No 1 District Depot in London ON. He was age 22 and single at the time.