Why Are the Toronto Blue Jays in the MLB’s American League?

The Toronto Blue Jays, the winners of the American League pennant, open the 2025 World Series as heavy underdogs against the Los Angeles Dodgers, the National League champs. 

Yes, you read that correctly; the Blue Jays of Toronto, Canada, will represent the American League in this year’s World Series. Baseball historians and fanatics know the Blue Jays have always been part of the American League since the birth of the franchise in 1977. But why they joined the New York Yankees, Boston Red Sox, and others in the AL instead of joining the only other Canadian team, the Montreal Expos, at the time in the National League, is less well known. 

The irony is not lost on me that Canada’s only MLB team is part of the American League, but it actually makes perfect sense. 

And, before we get started, it has nothing to do with the fact that the Expos, who left Montreal and became the Washington Nationals in 2005, were in the NL. MLB would not have cared to have two Canadian teams in the same league at the time. 

Instead, it has everything to do with the team the Blue Jays just beat in the 2025 American League Championship Series, my favorite baseball team, the Seattle Mariners. 

The Story Starts in 1969

Let’s take a little trip back to the summer of 1969. 

For that season, Major League Baseball selected two franchises, the Seattle Pilots and the Kansas City Royals, to expand the American League to 12 teams, along with the Yankees, Red Sox, Washington Senators, Baltimore Orioles, Cleveland Indians, Detroit Tigers, Chicago White Sox, Minnesota Twins, California Angels, and the Oakland Athletics. 

In 1970, the Seattle Pilots went bankrupt, which forced the move of the team to Milwaukee, where they became, and still are, the Milwaukee Brewers. 

Years later, in 1977, because of a lawsuit, MLB gave Seattle another crack at a franchise, dubbed the Seattle Mariners, but there was one problem. The Seattle Mariners were the AL’s 13th franchise, which would cause an imbalance in the team’s two divisions. It wasn’t the biggest problem in the world, but MLB decided to add another franchise to help rebalance the AL. 

A year earlier, the Toronto ownership group tried to buy and move the franchise from San Francisco to Toronto, but the deal fell through. Still, MLB saw an opportunity in awarding a team to the city of Toronto, a city with a pretty rich history of supporting baseball. And that team became the Toronto Blue Jays. 

The Blue Jays and Mariners Become Part of the MLB

The Seattle Mariners and Toronto Blue Jays officially joined MLB and the AL in 1977, and the rest is history. The Blue Jays have won two World Series titles and are playing for a third, while the Mariners’ best chance ever to make the World Series just slipped through their fingers thanks to the Mariners’ archnemesis, former Houston Astros star George Springer. 

So, in short, all of those Blue Jays’ fans rubbing it in Mariners’ fans’ faces because of how Game 7 of the 2025 ALCS played out need to remember one important thing. Without the Seattle Mariners, there’s no Toronto Blue Jays—not in their current form anyway.