A Métis, Firth was the first Indigenous politician from the North to win a seat in the House of Commons of Canada.
He served as the New Democratic Party Member of Parliament for the Northwest Territories during the 1970s.
He did not run for re-election in 1979, but attempted to return to the House of Commons in the 1980 election.
In private life, Firth had various careers as an airplane pilot, flying instructor, broadcaster and fur trader.
Firth made another attempt to return to the House of Commons in the 1997 federal election, this time running as an Independent in Western Arctic, but was again unsuccessful.