Oprah Winfrey announced Friday that her powerhouse daytime television show, the foundation of a multibillion-dollar media empire with legions of fans, will end its run in 2011 after 25 seasons on the air. Winfrey planned to announce the final date for “The Oprah Winfrey Show” during a live broadcast, according to her production company, Harpo Productions Inc. Once a local Chicago morning program, the production evolved into 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 US alone. “The Oprah Winfrey Show,” which is currently syndicated in 145 countries, has transformed Winfrey into a cultural phenomenon. She is credited with changing the way people talk to each other, having popularized a confessional interview style that has coaxed secrets, revelations and often tears from guests of all stripes. She has questioned some of the world's most famous people and has earned a reputation for being able to score the most highly sought-after interview subjects. Born into poverty in Mississippi, Winfrey is now estimated to be worth $2.7 billion and is regularly ranked among the world's most powerful women, celebrities and media personalities. Winfrey, 55, 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 about 74 million homes. An OWN spokeswoman declined comment Thursday. CBS Television Distribution, which distributes “The Oprah Winfrey Show” to more than 200 US markets, held out hope it could continue doing business with Winfrey. Winfrey's 24th season opened this year with a bang, as she drew more than 20,000 fans to Chicago's Magnificent Mile for a block party with the Black Eyed Peas. She followed 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 and Republican vice presidential candidate Sarah Palin. The show covered ranged from interviews with the world's celebrities to an honest discussion about Winfrey's weight struggles. In 1986, pianist-showman Liberace gave his final TV interview to Winfrey, just six weeks before he died. In a 1993 prime-time special, Michael Jackson revealed he suffered from a skin condition that produces depigmentation. Tom Cruise enthusiastically declared his affection for the much-younger Katie Holmes on the program in 2005 - and jumped on the couch to prove it. In 2004, Winfrey unveiled her most famous giveaway, when nearly 300 members of the studio audience opened a gift box to find the keys to a new car inside. The stunt became a classic show moment as much for Winfrey's reaction - “You get a car! You get a car! You get a car! Everybody gets a car!” - as its $7 million price tag. The show also became a launching pad for Oprah's Book Club, which then launched best-sellers. The titles ranged from “Song of Solomon” and “Paradise” by Toni Morrison to Wally Lamb's “She's Come Undone” and Elie Wiesel's “Night.” Powered by the show's staggering success, Winfrey built a media empire. Harpo Studios produces shows hosted by Dr. Phil McGraw and celebrity chef Rachael Ray. O, The Oprah Magazine was the nation's 7th most popular magazine in the first half of 2009. She is also credited with breaking down barriers as both a woman and an African-American and Forbes magazine declared her the first female African-American billionaire in 2003. She worked to overcome a painful history of child sexual abuse, supporting charities that help abused children and fighting for a national criminal database. Former president Bill Clinton signed the database into law in what was known informally as the “Oprah Bill.” In 2008, she broke with a precedent of staying out of politics and endorsed fellow Chicagoan Barack Obama's presidential bid. Her support was estimated by University of Maryland researchers to have brought in a million additional votes and helped Obama win the presidency.