He graduated from the St. Mike's Majors of the OHA in 1945. He turned pro the following year and joined the Tulsa Oilers of the USHL to serve the customary apprenticeship of the day. But the following year, Leafs' GM Conn Smythe launched a rebuilding campaign on behalf of his club. He brought names like Howie Meeker, Gaye Stewart, Gus Bodnar, and Joe Klukay into the fold. He also elected to take a chance with a couple of young defenders, Jim Thomson and Mortson. The two caught on, Thomson the stay-at-home defender and Mortson the flashier, whirling rusher who had a nose for trouble and abrasive play. The two became known as "The Gold Dust Twins."

Over the six years that followed, the "Twins" served as a defensive foundation during a great run for the Leafs as they captured Stanley Cup victories in 1947, 1948, 1949, and 1951. In 1952, however, the Leafs were in need of first-string goaltender. They managed to pry Harry Lumley away from the Blackhawks in exchange for Cal Gardner, Al Rollins and Mortson.

In the Windy City, Mortson continued his rough-house ways, lasting with the club for a total of six campaigns. By the close 1956-57 season, his villainy was confirmed as he led the league in penalty minutes for the fourth time in his career. In 1958, he was traded to his arch rivals, the Detroit Red Wings, where he concluded his NHL career at the end of the season.

Afterwards, he embarked on a lengthy minor-league stint with stops in Buffalo, Chatham, and Oakville. He finally called it a day in 1966.

Courtesy of the Hockey Hall of Fame