The curious location on Catalina Island stemmed from Cubs owner William Wrigley Jr.'s then-majority interest in the island in 1919. Wrigley constructed a ballpark on the island to house the Cubs in spring training: it was built to the same dimensions as Wrigley Field. (The ballpark is long gone, but a clubhouse built by Wrigley to house the Cubs exists as the Catalina County Club.) However, by <answer>1951</answer> the team chose to leave Catalina Island and spring training was shifted to Mesa, Arizona. The Cubs' 30-year association with Catalina is chronicled in the book, The Cubs on Catalina, by Jim Vitti . . . which was named International 'Book of the Year' by The Sporting News.
When did the Cubs choose to leave Catalina Island?
1951