Mr John Haggan was born on Constance Street in Belfast, Ireland (modern-day Northern Ireland) on 11 April 1877. 

He was the son of Belfast City natives Edward Haggan (b. 1856), a seaman, and Mary McGee² (b. 1858) who had been married in St Anne's Church, Belfast on 14 January 1876.

John's siblings were: Agnes (b. 29 May 1879)³, James (b. circa 1882)⁴, Edward (b. 23 January 1884)⁵, Sarah (b. 17 March 1886)⁶, Eliza Jane (b. 17 November 1888)⁷, Samuel (b. 19 November 1891)⁸ and Mary Ann (b. 8 January 1894).

In the late 1890s, John joined the Royal Horse Artillery and served during the Boer War. In 1901, he was part of the procession at Queen Victoria's Funeral.

John does not appear on the 1901 census of Ireland, but his parents and siblings were listed as residents of 49 Thorndyke Street, Pottinger, Belfast and indicated to be of Anglican religious background. On the 1911 census, John is shown living at 53 Thorndyke Street, Pottinger, Belfast, the home of his younger brother James and his profession was listed as shipyard labourer. His parents and other siblings were listed at 22 Thorndyke Street, and both households indicated that they were from a Presbyterian background.

John initially signed on to the Titanic in Belfast for the delivery trip to Southampton. When he signed on again in Southampton on 6 April 1912, he gave his address as the Sailors' Home, Southampton. His previous ship had been the Braehead, and as a fireman, he received monthly wages of £6. Also serving aboard was a neighbour from the same street, fellow stoker William Murdock.

Haggan survived the sinking (in which boat is uncertain, possibly boat 3). He returned to England on the Lapland shortly after the Carpathia arrived in New York City and was not called to give evidence to either the British or American Inquiries into the sinking.

John, who did not like to discuss the Titanic disaster, continued to live in Belfast, surrounded by his extended family. He never married and later lived at 49 Thorndyke Street, East Belfast. His father died 26 April 1928 and his mother on 16 February 1929.

John Haggan died in the Royal Victoria Hospital on 13 January 1952, aged 74 and following heart failure and pneumonia. He was buried in a family plot (C4-670/C4-671) with his parents and several of his siblings in Dundonald Cemetery, Dundonald, Co Down.