Alexander Bruce was born in Aberdeen, Scotland, probably in 1838 or 1839, the son of a master mariner. His parents' names are unknown. He worked 2½ years as a page in the service of Lord Lindsay and then completed an engineering apprenticeship with Blackie Brothers, Aberdeen. Before emigrating to New Zealand in 1863 he worked in Glasgow and at Blackwall Company's shipbuilding works, London. He married Mary Teasdale in Auckland on 27 April 1866, and they had 10 children. He died in Auckland on 14 July 1917.
Bruce arrived in Auckland on the ship Scimitar in March 1864, under engagement to the foundry firm of Vickery and Masefield (later Masefield and Company). He had joined the Amalgamated Society of Engineers in Aberdeen in 1861, and after his death it was claimed that he had come to New Zealand with a charter to form a branch of this society, and that he had established the branch in Auckland. In fact an ASE branch had been founded in Auckland on 29 May 1863 after agitation for an eight hour working day at Vickery and Masefield's. It is likely that the general secretary of the ASE in London, learning that Bruce was about to emigrate, asked him to take out the charter to the newly formed Auckland branch.
This charter is preserved in the Auckland office of the Engineers' Union. The union also has a photograph of Bruce, and his ASE badge. The inscription claims Bruce as the first secretary of the Auckland branch, from 1864 to 1884, but this is incorrect. Bruce was, however, an active member and served as secretary for lengthy periods in the 1890s and after the turn of the century. When Auckland unionists formed a trades council in 1876, Bruce was elected vice president, and was prominent in the early trade union movement in Auckland.
From Vickery and Masefield's Bruce moved to the other major engineering firm in Auckland, Fraser and Tinne's Phoenix Foundry. There he became involved in a strike over wage rates in 1866 and lost his employment. He then started a bakery and confectionery business with his brother-in-law, but three years later he departed for the Thames goldfields. He had little success in the search for gold, but was able to find work as an engineer, erecting quartz-crushing machinery. On his return to Auckland he rejoined Masefield and Company where he worked as a patternmaker until his retirement.
Bruce was active in local government. In 1884 he gained election to the Northcote Road Board. Later he became a member of the Waitemata County Council, and served as chairman for nine years. When Northcote was established as a separate borough in 1908, Bruce became its first mayor. A street in the borough bears his family's name. Bruce was a member of the Auckland Hospital and Charitable Aid Board for many years from 1893 and chairman from 1899 to 1901. In 1899 he was appointed a justice of the peace.
As a local politician Bruce was said to be painstaking and consistent, enjoying the utmost confidence of his constituents. There may have been some communication problem, however, for, according to a grand-daughter, 'he spoke so Scottish, us kids couldn't understand him half the time'.