At 14, Rankin dropped out of secondary school to work in a bakery and through the trade union he got involved in politics. During World War Two he served in the Canadian Army with Vancouver's Seaforth Highlanders of Canada. He attained the rank of sergeant and was wounded on 23 May 1944 during the Battle of the Hitler Line.
Rankin married a Jewish divorcee, and they had a son, Phil Rankin, who went on to become a Vancouver lawyer.
A documentary film, the Rankin File, was premiered in 2018, which was a biography and a background to the 1986 Vancouver mayoral election between Harry Rankin and Gordon Campbell.
After the war he completed his secondary education and pursued undergraduate studies at the University of British Columbia, where he also earned a law degree. During his time at U.B.C., he joined the Communist University Club, briefly serving as its vice-president.
Communists were banned from joining the bar and the Law Society of British Columbia interviewed Rankin at length prior to admitting him to the bar about his views on God, whether he would defend his country if attacked, and whether he was a member of the Communist Party of Canada, then called the Labor-Progressive Party, something he was able to deny as the Communist University Club was an independent and unaffiliated organization. In the wake of the Law Society refusing to admit Gordon Martin to the bar on account of his being an avowed communist, Rankin had to sign a declaration that he was not a communist prior to being allowed to join. He went on to become head of the Law Society in 1979 (a position then known as Treasurer, later known as President).
As a lawyer, Rankin fought for and helped establish the province's legal aid system. In 1950 he was one of the founding members of a committee that created a list of lawyers who were willing to take on cases, mostly pro bono, preceding the establishment of the BC Legal Aid Society by 20 years.
Rankin ran for office more than a dozen times before being elected to the Vancouver City Council in 1966 as the sole independent alderman on a council dominated by the conservative Non-Partisan Association. Vancouver's aldermen were elected through an "at large" system rather than by ward meaning voters from wealthier neighbourhoods were able to monopolise council elections and that only candidates who could afford a citywide campaign had a chance of being elected. Rankin helped form the Committee of Progressive Electors (COPE) as a left wing civic political party and it subsequently pushed for a ward-based electoral system to be introduced in Vancouver, culminating in a referendum in October 1973, at which the ward proposal was defeated.
Rankin was a 20-year veteran of city council when he ran for mayor in 1986, losing to Gordon Campbell. He returned to city council as an alderman in the subsequent election and remained on the body until his retirement from politics in 1993.
He died on February 26, 2002, from a heart attack, aged 81.
Rankin's widow, Connie Fogal, is the former leader of the Canadian Action Party. Rankin's son, Phil Rankin, continues in his father's footsteps as a lawyer and advocate for legal aid. His grandson, Micah Rankin, is a law professor at Thompson Rivers University. His nephew, Lee Rankin is a lawyer and was a long-time councillor in Burnaby, British Columbia and was a federal Liberal candidate in 2000 and a BC Liberal candidate in the 2009 provincial election.
- Roy, Reginald H. (1969). Seaforth Highlanders of Canada 1919-1965. Evergreen Press, Vancouver.
- Zuehlke, Mark (July 2009). Ortona: Canada's Epic World War II Battle. ISBN 9781926706023.
- Rankin, Harry (1975), Rankin's Law: Recollections of a Radical, Vancouver: November House, p. 60
- Rankin, Harry (1975), Rankin's Law: Recollections of a Radical, Vancouver: November House, p. 63
- Rankin, Harry (1975), Rankin's Law: Recollections of a Radical, Vancouver: November House, p. 70
- "Presidents and Treasurers, 1869 to present". The Law Society of British Columbia. 2014. Archived from the original on 23 October 2014.
- Rankin, Harry (1975), Rankin's Law: Recollections of a Radical, Vancouver: November House, p. 85
- Rankin, Harry (1975), Rankin's Law: Recollections of a Radical, Vancouver: November House, p. 130
- Rankin, Harry (1975), Rankin's Law: Recollections of a Radical, Vancouver: November House, p. 179
- Tom Hawthorn (5 March 2002). "From gadfly to icon of B.C. politics". The Globe and Mail. Internet Archive. Archived from the original on 20 January 2003. Retrieved 17 November 2011.
- Rankin, Harry (1975), Rankin's Law: Recollections of a Radical, Vancouver: November House, p. 112
- "BC trial lawyers withdraw services to draw attention to 'dire' legal aid funding | the Hook, A Tyee blog". 15 November 2012.
- "6 potential candidates for Team Trudeau following Karen Wang fiasco in Burnaby South". 17 January 2019.