A member of the "Original Six", the club was founded in 1917. The franchise did not have an official name, but was informally called "the Blueshirts" or "the Torontos" by the fans and press. Under new ownership, the club was renamed the Toronto St. Patricks in 1919. In 1927, the club was purchased by Conn Smythe and renamed the Maple Leafs.

Under manager Charlie Querrie, and head coach Dick Carroll, the team won the Stanley Cup in the inaugural 1917-18 season.

Tim Horton was called "Superman" by goaltender Johnny Bower, who claimed the defenseman and longtime teammate could lift a filled 40-gallon oil drum. Another teammate, center Dave Keon, recalled that Horton could throw around railroad ties "like they were toothpicks." Fellow Toronto defenseman Bob Baun saw him barricade an intersection in Quebec as a prank by lifting barrels of cement. Gordie Howe of the Detroit Red Wings, hardly a weakling himself, called Horton "the strongest player in hockey."

On February 7, 1976, in an 11-4 win over the Boston Bruins at Maple Leafs Garden in Toronto, Darryl Sittler scored 10 points--the greatest individual performance in the history of the NHL.

In 1977, the NHL began to mandate nameplates on the back of jerseys for the sake of player recognition to both the fans and broadcasters. Harold Ballard wasn't a fan of the idea, so he made the letters the same colour as the uniform.

During a brawl, Hadfield got hold of Bernie Parent's mask and donated it to the Madison Square Garden crowd, forcing Parent out of the game. Garden police did their best to recover the mask, but the fans weren't interested: it was, as The New York Times noted, "passed along, bucket-brigade style, around half the Garden" as appeals for its return rang from the arena PA.

Howie Meeker scored 27 goals and 45 points during his rookie season, beating out "Mr. Hockey" (7 goals and 22 points) for the Calder Memorial Trophy. Meeker also played in the 1947 NHL All-Star Game and tied an NHL record for most goals by a rookie in one game with five goals against the Chicago Black Hawks.

In his first full season with the Maple Leafs, 1992-93, Doug Gilmour had the finest season of his career, setting franchise records for assists (95) and points (127), and tying Babe Pratt's franchise record by assisting on six goals in one game.

Ace Bailey was the NHL's leading scorer in the 1928-29 season, with 22 goals and 32 points in 44 games. He was again the Leafs' leading scorer in 1929-30 and one point short of repeating in 1930-31. In 1932, he helped Toronto win the Stanley Cup, scoring the Cup-winning goal in game 3 of the finals. But his career came to an abrupt end on December 12, 1933, when a hit from behind by Eddie Shore of the Boston Bruins fractured his skull and left him convulsing on the ice. Bailey spent ten days in a coma. Although he eventually made a full recovery, he never played another game. On February 14, 1934, his #6 jersey became the first number officially retired in all of professional sports.

Red Horner retired as the NHL's all-time penalty minutes leader, a mark he held until "Terrible Ted" Lindsay broke it in the late Fifties.