Article: 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 1951 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.

Question: What did Wrigley construct on the island to house the Cubs in Spring training?
a ballpark