Thomas McEwen was born in Scotland and moved to Canada in 1912. A blacksmith by trade, he was active throughout his life in the labour movement and as a member of the Socialist Party of Canada and its successor, the Communist Party of Canada. He was also Secretary-General of the Workers' Unity League before its demise in 1936. Between 1931 and 1944, he was imprisoned for seven years for his communist activities. In 1944, McEwen began his career as a newspaper editor, first with the Yukoner and later with the Pacific Tribune in British Columbia. He also ran unsuccessfully in the 1945 federal election as a labour candidate in the Yukon.