MacKay was born in Chesley, Ontario on May 21, 1894, the son of John MacKay and Margaret McMillan.

He married Anne May Reyburn on June 12, 1916 in Grand Forks, B.C.

MacKay played professional hockey for several teams: Vancouver Millionaires, Chicago Black Hawks, Pittsburgh Pirates, and Boston Bruins.

He was part of two Stanley Cup winning teams: The Vancouver Millionaires in 1915 and the Boston Bruins in 1929. He was inducted into the Hockey Hall of Fame.

MacKay died after having a heart attack while driving and crashing his car near Nelson, British Columbia.

He was buried in Evergreen Cemetery, Grand Forks, B.C.

Source: https://www.wikitree.com/wiki/MacKay-3053

He joined the Canadian Army at the age of 14 and briefly trained at the Valcartier training camp in Quebec until recruiting officers realized he was under age and discharged him from the service.

He played with the Chesley Ontario senior OHA in 1911, then moved to Edmonton for the 1912-13 season, and played for the Edmonton team which won the city championship.

Then he moved to Grand Forks, and played there during the 1913-14 season, winning the McBride Cup, and the Daily News Cup, for the Kootenay championship; and the Boundary Cup, for the Boundary Championship.

He was known as a phenom then, and he was signed by Vancouver for the 1914-15 season, although his residence had shifted for a time to Toronto. At the of time of joining Vancouver, he was considered the youngest professional hockey player at 19.

Source: Craig H. Bowlsby, Empire Of Ice: The Rise and Fall of the Pacific Coast Hockey Association, 1911-1926, p.358

With the senior team in Grand Forks, he was the provincial league’s leading goal scorer with 15 goals in 1913–14. Source: https://peoplepill.com/people/mickey-mackay

MacKay learned to skate at the age of 15.

While with the Edmonton Dominions of the Alberta Senior Hockey League, in 1912-1913 he led the league with eight playoff goals, and was a teammate of future Vancouver Millionaires teammate Barney Stanley.

A marvelous skater and goal scorer, Duncan “Mickey” MacKay was blessed with instinct and timing on the ice that was matched by few contemporaries. A star rover and center in a number of leagues during his career, he was particularly successful in the Pacific Coast Hockey Association, where his offensive heroics made him one of the Vancouver Millionaires’ most popular stars.

In 1914 McKay was signed by the Vancouver Millionaires of the PCHA and he quickly embarked on the most fruitful period of his hockey career. MacKay dazzled the West Coast fans with a three-goal effort in his first league game on December 8, 1914, playing on a line with Frank Nighbor and Ken Mallen. His 33 goals in 17 games as a rookie exceeded all other rivals. During the Stanley Cup victory over Ottawa, MacKay continued to impress with four goals in the three-game series that his team dominated.

The scoring exploits of MacKay didn’t abate during the coming years. He was sensational during Vancouver’s heartbreaking loss to the Toronto Arenas in the 1918 Stanley Cup series, scoring five goals in as many games playing as a rover and right wing.

“The Wee Scot” spent the 1919-20 schedule with the Calgary Columbus of the Alberta Big 4 Hockey League before returning to Vancouver the next year. He topped the PCHA in goals scored during its last year of operation in 1923-24. That same year his Vancouver squad lost to the Montreal Canadiens in the last Stanley Cup championship series involving a PCHA team.

The Vancouver franchise joined the Western Canada Hockey League in 1924-25 and MacKay led the way on the strength of a league high of 27 goals in 28 games. The loop was renamed the Western Hockey League prior to the 1925-26 schedule. When the league folded a few months later, MacKay was among the stars coveted and purchased by NHL teams. Consequently he joined the Chicago Black Hawks for their inaugural season in 1926-27. MacKay spent two years in the Windy City recording 31 goals playing on a line with Dick Irvin.

Acquired by the Pittsburgh Pirates in the off-season, MacKay was traded again, this time to the Boston Bruins, on December 21,1928. He scored nine goals while helping the Bruins finish at the top of the American Division standings. In the Stanley Cup finals, MacKay helped the Beantowners quell the New York Rangers in two straight games and got his name on the Cup for the second time in his career. He retired as a player partway through the next season to assume the task of business manager with the Bruins.

MacKay scored 260 regular-season and playoff goals in three top-flight leagues between 1914 and 1929.

Source: https://www.hhof.com/HonouredMembers/MemberDetails.html?type=Player&mem=p195205&list=

MacKay was regarded by his contemporaries as one of the top players of his time. 

Lester Patrick praised his abilities:

“He was perhaps the greatest center we ever had on the coast. MacKay was a great crowd pleaser. He was clean, splendidly courageous, a happy player with a stylish way of going. He was one of those who helped make pro hockey a great game.”

His greatest limitation was his size, standing five foot nine and around 162 pounds; he frequently battled through injuries and missed many games throughout his career as a result. His nickname, “the wee Scot”, was in reference to his diminutive size.

Leaving the Bruins, MacKay settled near his wife’s hometown of Grand Forks. He remained active in hockey, serving as a referee and coach in the area.

He contemplated purchasing the Spokane Clippers of the minor professional Pacific Coast Hockey League in 1938 but decided against taking over the team. MacKay became involved in mining in the eastern Kootenays upon his return to British Columbia.

He died on May 30, 1940, when traveling as part of his mining job after his vehicle left the road and hit a telephone pole near the village of Ymir. The medical examiner determined that he had suffered a heart attack, causing the crash.

MacKay was posthumously honored by several organizations for his hockey career, and was inducted into the Hockey Hall of Fame in 1952. He was inducted into the British Columbia Sports Hall of Fame in 1989, and is an honored member of the British Columbia Hockey Hall of Fame. Source: https://en.wikipedia.org/wiki/Mickey_MacKay