In 1981, after 6 decades under the Wrigley family, the Cubs were purchased by Tribune Company for $20,500,000. Tribune, owners of the Chicago Tribune, Los Angeles Times, WGN Television, WGN Radio and many other media outlets, controlled the club until December 2007, when Sam Zell completed his purchase of the entire Tribune organization and announced his intention to sell the baseball team. After a nearly two-year process which involved potential buyers such as Mark Cuban and a group led by Hank Aaron, a family trust of TD Ameritrade founder Joe Ricketts won the bidding process as the 2009 season came to a close. Ultimately, the sale was unanimously approved by MLB owners and the Ricketts family took control on October 27, 2009.

What company purchased the  Cubs in 1981?