He began playing minor hockey in Galt, Ontario, and was offered a chance to officiate games.
His one major injury came in 1971 when Philadelphia Flyers player Gary Dornhoefer fell along the boards, and knocked Armstrong up against the glass.
Dornhoefer's stick cut Armstrong's hand and broke a bone, forcing him to wear a cast for three months.
On October 16, 1973, Armstrong was honoured in a ceremony at the Detroit Olympia for officiating his 1,314th game, which broke the previous record set by George Hayes.
Following his tenure with Dallas, Doug became the executive vice president and general manager of the St. Louis Blues and won the Stanley Cup in 2019.