Media conglomerate Tribune Co. announced a definitive agreement yesterday to sell all but a 5 percent stake in the Chicago Cubs and Wrigley Field to the billionaire Ricketts family, capping a tortuous process that began nearly 2 1/2 years ago.

Tribune valued the transaction at about $845 million.

"Our family is thrilled to have reached an agreement to acquire a controlling interest in the Chicago Cubs, one of the most storied franchises in sports," said Joe Ricketts, who founded the Omaha, Neb.-based online brokerage TD Ameritrade Holding Corp.

Tribune had announced on Opening Day in 2007 that the marquee baseball franchise and historic ballpark would be sold at the end of that season. But the process was slowed by CEO Sam Zell's efforts to maximize sale profits, the collapse of the credit markets and Tribune's 2008 bankruptcy filing.

The Ricketts family, tentatively selected as the winning bidder last January, had agreed to pay about $900 million for the team, Wrigley and a 25 percent stake in Comcast SportsNet Chicago, which broadcasts many Cubs games. But that total was renegotiated, with Tribune retaining a small stake for legal reasons.

The sale figure exceeds the record $660 million paid for the Boston Red Sox in 2002, although that deal did not include a ballpark.

Chicago-based Tribune bought the Cubs in 1981 from candy maker Wm. Wrigley Jr. Co. for $20.5 million. Zell, a real estate mogul, engineered a takeover of Tribune in 2007 - but might not remain for long as head of the company, which also owns the Los Angeles Times, the Chicago Tribune, other major U.S. newspapers, two dozen TV stations and Chicago radio station WGN.

Randy Michaels, the company's chief operating officer, said in a note Thursday to employees that "the ownership structure of the company is likely to change."

Noteworthy

* The Nationals introduced their top draft pick, San Diego State pitcher Stephen Strasburg, at a news conference held on the field that was open to any fans who wanted to come to the ballpark early. A few hundred fans took the bait, no doubt motivated by the offer of $1 tickets.

Because he has not pitched competitively since the college baseball season ended last spring, the club will send him to Florida to build up his arm, with his major league debut expected next year.

The No. 1 overall draft pick agreed Monday night to a contract that guarantees him $15.1 million over 4 years.

In games last night:

* At Washington, Prince Fielder and Casey McGehee homered, and the Milwaukee Brewers beat the Nationals, 7-3. Braden Looper (11-6) allowed two runs over six innings for the Brewers.

* At San Diego, Nick Hundley hit a three-run homer and Clayton Richard won his third straight decision to lead the Padres to a 4-0 win over the St. Louis Cardinals.

* At Pittsburgh, Garrett Jones and Lastings Milledge homered and the Pirates beat the Cincinnati Reds, 5-2, for their fourth straight victory.

* At Houston, Roy Oswalt (7-4) allowed three hits in seven innings and Jeff Keppinger's double in the fifth inning drove in the game's only run as the Astros edged the Arizona Diamondbacks, 1-0. *