Armstrong was born in Kingston, Nova Scotia, the son of James Armstrong and Elizabeth Pearce,[2] both Baptists of loyalist descent.[3] He was educated at the Pictou Academy, Acadia College, the Manitoba Medical College, and King's College Hospital in London, UK. He received a Bachelor of Arts degree from Acadia, and medical certification from the MMC. Armstrong worked as a physician and surgeon, and was also president and director of the Gladstone Telephone and Electric Light Company.