The queen of daytime talk will relinquish her network television throne Wednesday to oversee the rest of her sprawling kingdom, which has extended its reach to film, Broadway, publishing, politics, cooking, fitness, the self-help industry, a fledgling cable channel and the throbbing crannies of America’s heart.

“The Oprah Winfrey Show,” one of the most durable and top-rated programs in TV history, is ending its quarter-century run with fanfare worthy of a president or pope — or of a woman born into poverty in Mississippi who built a media empire around her own nationally syndicated talk show.

“The adversity of her childhood somehow gave her a sense of confidence, a sense of empowerment and a desire to help, and that’s part of her basic persona,” says Barbara Walters, who has interviewed Winfrey, 57, on multiple occasions. “I think Oprah is a superb performer. . . . She has this amazing capacity to relate to an audience, which made her a star almost from the day she started to broadcast. It’s in her magazine and it’s in everything she does. She talks about herself, she touches the audience and they become almost one with her.”

That oneness has fueled Winfrey’s show for 25 seasons, through 30,000 guests, a million studio audience members, legions of viewers in 150 countries, 48 Emmys and the Kennedy Center Honors. Her personal net worth is $2.7 billion, according to Forbes, making her the only female African American billionaire at present. She’s used her daytime platform to establish a production company (with projects in film, TV and XM satellite radio), a glossy national magazine (with 2 million subscribers) and a now-shuttered charity wing (which raised more than $80 million and constructed schools in South Africa).

Winfrey’s journey to the center of American consciousness started on Sept. 8, 1986. The first national episode of “The Oprah Winfrey Show” was titled “How to Marry the Man/Woman of Your Choice.”

Wednesday’s taped finale will be her 4,561st show, the last in a long line of episodes featuring aspiration as entertainment. With Oprah as its guide, the country learned how to find its dream partner, how to dance like Tina Turner, how to negotiate racism and religion-based fear. “Live your best life,” implores the cover of every “O” magazine, whose readers are 88 percent female.

“Speaking for those of us who were deeply involved in civil rights, she did more for African Americans than all of us put togther,” says Del. Eleanor Holmes Norton, who witnessed Winfrey’s efforts to raise funds for the National Council of Negro Women in the District. “A black woman becoming an icon of educated, working-class white women is beyond anything any of us could’ve hoped to do. You can’t love Oprah and hate black people. And when you consider how much drudgery is on television, to see this woman who stands for reading books, for making women think better of themselves, for making people feel guilty if they hated other people — she’s a phenomenon the likes of which this society has never seen.”

The cultural legacy of “The Oprah Winfrey Show” is at once intensely personal and too galactic to fathom.

Without “The Oprah Winfrey Show,” where would we be? We wouldn’t have T-shirt bedsheets, footless pantyhose or the “The Color Purple,” the musical. We wouldn’t have a council of chatty behavioral gurus upon whom Oprah has bequeathed fame and success: financial taskmaster Suze Orman, cooking sprite Rachael Ray, decor wizard Nate Berkus, and doctors Oz and Phil, who’ve made it their business to be in ours.

“Oprah” told us there is no shame in being the victim of sex­ual abuse. “Oprah” told us how to find our correct bra size.

Without “The Oprah Winfrey Show,” some of us would never have picked up Tolstoy or dropped 15 pounds (and then gained them back again). Without “Oprah,” we, as a country, would not be talking about so many issues so candidly, according to CBS chief executive Leslie Moonves.

“We wouldn’t have nearly as much of the dialogue we have throughout America about what’s happening in our society,” says Moonves, whose CBS Corporation distributes the show. “She sort of introduced what the world was like and let people think and talk and go from there. . . . I think it allowed other morning shows — including ‘The Early Show,’ and the ‘Today’ show and ‘Good Morning America,’ which preceded her — to change their dialogue, to be more frank, more conversational, more relatable. It wasn’t ‘I’m going to tell people things’ as opposed to ‘I’m going to open the dialogue.’ ”

So let’s talk, America. An Oprah-size hole is about to appear in daytime television. How do you feel?

“I don’t remember a time without Oprah,” says District resident Jennifer Christian, 26, as she got a pedicure at Patsy’s Nail Bar at 20th and I streets NW onTuesday afternoon while the penultimate “Oprah” show played on a TV. “She’s a strong female role model who transcends generations.”

“I think she’s a strong, empowered female hero,” said Christian’s mother, Diane, as Jerry Seinfeld paid tribute to Winfrey onscreen. “And she is kind and empathetic to the people around her.”

Oprah positioned her show at the vanguard of national discourse. Oprah was talking about AIDS on national television in 1987. Oprah, newly svelte in 1988, wheeled out 67 pounds of fat on a Radio Flyer wagon, launching the national pastime of battling lard in a public forum (see: “The Biggest Loser”). Oprah was moved to tears by non-famous guests such as her fourth-grade teacher, the woman with 92 personalities and the 12-year-old with muscular dystrophy. Oprah gleefully bellowed the names of celebrity friends who’d stop by for a safe-zone chat (“JOHN TRAVOLTAAA!”), and showered audiences with expensive gifts donated by major corporations (“You get a car! You get a car!”).

America, though, has been slowly turning away from Oprah, or at least Oprah’s time slot. An average of 12.6 million people watched each episode during her peak season, 1991-92. This past season the number was just over 6 million — still topping other daytime progams but eroding alongside soap operas, as networks fend off the creep of cable TV by scheduling reality shows and ensemble gabfests like “The View” and “The Talk.”

But “The Oprah Winfrey Show,” for all its longevity, was merely the root system for the flowering of the Oprah brand, embodied by a question that a follower might ask herself in a moment of uncertainty: “What would Oprah do?”

She’d read Faulkner. Over the past 10 years Oprah’s Book Club — which restored classics to the bestseller lists and plucked new talent from obscurity — generated 22 million sales of specially branded editions of her selections.

What would Oprah do?

She’d eat hickory-smoked turkey from East Texas. Soon after she featured a turkey supplier on her annual “Favorite Things” show in 2003, the company rang up $1 million in sales, according to Bloomberg Businessweek.

What would Oprah do?

She’d vote for Barack Obama. Her May 2007 endorsement delivered Obama an “instrumental” 1 million votes over the competitive Democratic primary season, according to Northwestern University marketing professor Craig Garthwaite, who co-wrote a 2008 study on celebrity endorsements in politics.

“The Oprah Winfrey Show” has wrested the concept of women’s empowerment from feminists and put it in the hands of the masses, according to Marjorie Jolles, a professor of women’s and gender studies at Roosevelt University.

“I would even call it a spiritual empowerment,” Jolles says. “I see Emerson as her main rhetorical ancestor, in thinking that the individual is something that unfolds in a divinely-inspired way.”

Oprah’s own sense of destiny — “I have always known that I was born for greatness in my life,” she told Walters in 1988 — has made her the subject of adoration as well as derision and skepticism.

“She believes more in inspiration and enlightenment, when the science shows people need specific behavior change — her legacy is what I would call conscious-raising and awareness-inducing, but not behavior-changing,” says John Norcross, a professor of clinical psychology at the University of Scranton who was scheduled to appear on Winfrey’s show to challenge her endorsement of “The Secret,” a 2006 self-help book that linked positive thinking to real-world results. (His appearance was canceled after the book’s author declined to participate, according to Norcross.)

Winfrey’s commanding onscreen presence has inspired parodies of her pomposity and wealth on sketch shows like “Saturday Night Live” and “MADtv.” Her show was such a rich source of comedy because “she is a deity and reminds us of it,” says comedy Kathy Griffin, who regularly lampoons Winfrey in her stand-up act. “Even while she’s doing an incredible act of goodwill, she’s so over-the-top.”

In a final act of Oprahness, it seems as though Oprah was her own last guest, according to audience members interviewed by the Chicago Tribune after the finale’s taping Tuesday.

But with the Oprah Winfrey Network barely six months old, “final” and “last” aren’t in Winfrey’s vocabulary. In the mind-over-matter physics of her universe — which is our universe — “the end” is always just “the beginning.”

Staff writer Vanessa Williams contributed to this report.