The answer is 42

Today is remembered in baseball as Jackie Robinson Day, the day in 1947 when he was called up to the Brooklyn Dodgers. However, what most people don't know is that his first game on an integrated team was not with the Dodgers. A year and a half earlier, in October 1945, he joined the Dodgers' farm team, the Montreal Royals. Yep, Jackie Robinson's first non-Negro League team was Canadian. It wasn't always easy, particularly during spring training in Florida, but he was a hometown hit in La Belle Ville. In the 1946 season, over a million tickets were sold to Royals games (probably more than the major-league Expos sold in all their 35 years in Montreal).

(A one-minute dramatization of a Montreal Royals game with Robinson at bat)