[2] Before he was injured for the final time, he was elected as the secretary of his United Mine Workers of America (UMW) local.
[3] Muir began politics as a member of the Sydney Mines, Nova Scotia municipal council, where he served from 1948 to 1958.
[4] He entered federal politics in the 1957 Canadian general election, winning the Cape Breton North and Victoria electoral district in Nova Scotia.
[4] Muir then ran in the newly created Cape Breton—The Sydneys electoral district in the 1968 Canadian general election and won the seat.
[4][5] On 28 March 1979, two-days after an election call, Liberal Prime Minister Pierre Trudeau appointed Muir to the Senate.