The Oprah Winfrey Show, a groundbreaking broadcast that began as a local Chicago talk show and grew over two decades into the foundation of a media empire worth billions, will end its run in 2011 after 25 seasons on the air, Winfrey's production company said Thursday night.

Winfrey plans to announce the final date for her show during a live broadcast on Friday, Harpo Productions Inc. said, bringing an end to what has been television's top-rated talk show for more than two decades, airing in 145 countries worldwide and watched by an estimated 42 million viewers a week in the U.S. alone.

A Harpo spokeswoman declined to comment Thursday on Winfrey's future plans except to say that The Oprah Winfrey Show will not be transferred to cable television.

Winfrey is widely expected to start up a new talk show on OWN: The Oprah Winfrey Network, a much-delayed joint venture with Discovery Communications Inc. that is expected to debut in 2011. OWN is to replace the Discovery Health Channel and will debut in some 74 million homes. An OWN spokeswoman declined to comment Thursday.

CBS Television Distribution, which distributes The Oprah Winfrey Show to more than 200 markets blanketing the United States, held out hope that it could continue doing business with Winfrey, perhaps producing a new show out of its studios in Los Angeles.

"We have the greatest respect for Oprah and wish her nothing but the best in her future endeavors," the unit of CBS Corp. said in a statement. "We know that anything she turns her hand to will be a great success. We look forward to working with her for the next several years, and hopefully afterward as well."

Winfrey's 24th season opened earlier this year with a bang, as she drew more than 20,000 fans to the city's Magnificent Mile on Michigan Avenue for a Chicago block party with the Black Eyed Peas.

She followed up with a series of blockbuster interviews — Mike Tyson and Evander Holyfield, exclusives with singer Whitney Houston and ESPN's Erin Andrews, and just this week, former Alaska governor, GOP vice presidential candidate and best-selling author Sarah Palin. She found time between shows to lobby the International Olympic Committee in Denmark for Chicago's failed bid to host the 2016 Olympics.

The loss of The Oprah Winfrey Show would be a blow to CBS Corp. because it earns a percentage of hefty licensing fees from TV stations that use it.

On a conference call with analysts two weeks ago, CBS Chief Executive Leslie Moonves said the contract with the show ran through most of 2011 and "if there's a negative impact, it wouldn't hit us until '12."

CBS continues to sell several top shows into syndication, however, including Wheel of Fortune and Jeopardy. But many TV stations are struggling with falling advertising revenue and were unlikely to pay the same fees as in the past for Winfrey's show, which has seen ratings slip 7 percent from a year ago and saw its average viewership slip below 7 million last season.

Winfrey started her broadcasting career as a teenager in Nashville, Tenn., reading the news at WVOL. Two years later, Winfrey started co-anchoring news broadcasts on WTVF-TV in Nashville. In 1976 she moved to Baltimore to anchor newscasts at WJZ-TV before becoming host of the local talk show People Are Talking.

In 1984, she relocated to Chicago to host WLS-TV's morning talk show A.M. Chicago — the show became The Oprah Winfrey Show one year later. She set up Harpo the following year and her talk show went into syndication, rising to become one of the most successful in the history of broadcasting.

Powered by the show's staggering success, Winfrey built a wide-ranging media empire. Harpo Studios produces shows hosted by Dr. Phil McGraw and celebrity chef Rachael Ray, her "book club" selections produce instant best-sellers, and O, The Oprah Magazine was the nation's seventh most popular magazine in the first half of 2009.

"I came from nothing," Winfrey wrote in the 1998 book Journey to Beloved. "No power. No money. Not even my thoughts were my own. I had no free will. No voice. Now, I have the freedom, power, and will to speak to millions every day — having come from nowhere."

Earlier this year, Forbes scored Winfrey's net worth at $2.7 billion, even as the magazine knocked her from atop its list of the world's most powerful celebrities. The honor went to Angelina Jolie, but Winfrey was still No. 2 on the annual Celebrity 100 list — and the top earner at $275 million. (Source: NPR)