The first junior teams started play in 1892, without enforced age limits; the first champions Kingston Limestones over Galt.
Junior hockey now became age-limited to players 20 years of age or younger by January 1 of the season being played.
The end of World War I marked the beginning of the Memorial Cup, the symbol of junior hockey supremacy in Canada.
As each year passed, the number of communities participating in junior hockey grew and the calibre of play increased.
The 1930s gave birth to noted teams such as the Oshawa Generals, St. Michael's Majors and the Toronto Marlboros.
The 1940s welcomed new communities to the limelight such as the Barrie Flyers, Guelph Biltmore Mad Hatters, Stratford Kroehlers and the St. Catharines Teepees.
Stafford Smythe, owner of the Toronto Maple Leafs, started the Metro Junior A League in an attempt to rival the OHA.
The Toronto Marlboros, who were owned by the Leafs, were withdrawn from the OHA and placed in a league with promoted Junior B teams including the Whitby Mohawks, the Brampton 7 Ups, and the Unionville Seaforths.
The other member of the league was the former St. Michael's Majors franchise, who would be later transferred to Neil McNeil High School in Scarborough, Ontario.
Father David Bauer, the legendary coach and St. Michael's teacher, had decided to withdraw the private school from participation following their Memorial Cup win in 1961.
In response, the OHA managed to convince Sam Pollock's Montreal Junior Canadiens to join.
The league that year consisted of the Guelph Royals, Hamilton Red Wings, St. Catharines Black Hawks, Peterborough T.P.T., Montreal Junior Canadiens and the Niagara Falls Flyers.
When the NHL expanded in 1969, the rules of the draft were changed to allow any amateur player under the age of 20 to be chosen.
The OHA ceased being a direct farm system and began to compete with other junior leagues to graduate players.
The 1971 series featured future NHL stars Guy Lafleur and Marcel Dionne, but never lived up to the potential on ice brilliance that could have been.
This rivalry was further fueled by the desire of Francophone nationalists to have a Canadian champion from a Quebec team in a Quebec-based league.
The Remparts won the first game 4–2 played in St. Catharines and televised by closed circuit to over 8,000 spectators in Quebec arenas.
As the game wore on, more and more fights broke out on the ice, involving players leaving the penalty box to join the fray.
After the game an angry mob surrounded the St. Catharines team bus on its way to the motel, and was given a police escort to safety.
The parents of the St. Catharines players refused to send their children back to Quebec City for fear of the violence that occurred after game four.
The problem was further confounded with threats surfacing from the FLQ (Front de libération du Québec) against St. Catharines players.
CAHA president Dawson declared the series to be over when no further compromise could be reached, and he had received official notice from St. Catharines that the team would not return to the Colisée.
As a result, the Remparts went on to compete for the Memorial Cup by default, which they won, defeating the Edmonton Oil Kings.
The OHA then "re-established" the suspended franchise after a one-year hiatus, under new ownership and with new players, calling the team the Kingston Canadians.
Marie that had been part of the Northern Ontario Junior Hockey League (NOJHL) prior to the Tier I/Tier II split, joined the Major Jr. A ranks in 1972 to rejoin the Memorial Cup hunt.
The Kingston Canadians joined the OHL in their place as the Junior Canadiens' successors, albeit with different ownership and players.
The OMJHL instituted many rules changes to distinguish itself from Tier II (Minor Jr. A), including allowing one overage player on the roster.
In 1980, the Ontario Major Junior Hockey League sought to gain further independence and more control over its financial policies and gate receipts.
In the 1980s, the league added the Guelph Platers and Belleville Bulls, and welcomed the Cornwall Royals from the QMJHL.
The league continued to expand with two new teams in 1998; Don Cherry's Mississauga IceDogs and the Brampton Battalion.