To speak of Oprah Winfrey is to speak in hyperbole. Journalists, comics, celebrities, and even political leaders talk of her cultural power and influence like a historian might talk of the Caesars or Alexander the Great. The United States of America is a super-sized nation, so it should come as no surprise that it would create super-sized mythologies, from Paul Bunyan to Oprah Winfrey.

Winfrey’s biography is a great American story. Davey Crockett and the lads of Horatio Alger would, I think, have found her great company.

It’s kind of astonishing that Ms. Winfrey created her vast cultural empire from the modest raw material of a daytime talk show. She owes a lot to Phil Donahue, of course, who had developed the daytime form in radical ways, many of which Winfrey would adopt and adapt. Phil--with his candor, outspokenness, and graceful familiarity--was good; Oprah was even better.

Like Arthur Godfrey, Johnny Carson, Fred Rogers, and Walter Cronkite, Winfrey excelled on the small screen. She could talk to millions of people at once while giving the impression that she was having a conversation with you as she helped you fold the laundry.

Smart, savvy, and strong, Winfrey then used the base camp of her talk show from which to launch sorties into the vast cultural territories of the nation.

Publishing, producing, radio: she was good at all of it, even acting, delivering some remarkable performances in “The Color Purple” and “Beloved.” It was the talk show, though, that provided the daily nourishment and support for the emerging “branded lifestyle” that she was creating.

Winfrey’s message on that show was the oldest of American stories. From Plymouth Rock to the vast immigration waves of the late nineteenth and early twentieth century, America has always pushed the myth of reinvention and empowerment, becoming a new person in a new world. Winfrey repackaged that national epic into the terms of the daily lives of her viewers: dieting, managing relationships, going about the daily grind of the pursuit of happiness.

She may have been the greatest self-help advocate since Benjamin Franklin, and in being so, she very likely made the lives of many people, her audiences and the recipients of her philanthropy, better.

We should, however, take care in overestimating the influence of Winfrey. Yes, she did get a lot of people to buy (and some of those to actually read) some good books. But I’m not sure that she managed to turn us into a more literary society.

And I think Barack Obama would have been elected with or without her endorsement. 

The end of “The Oprah Winfrey Show” does not, of course, mean the end of Oprah Winfrey. She will likely be a media presence for as long as she is able and wants to be one. But this may be the end of the “Age of Oprah,” if there ever was such an age.

Her daily show was the source of her influence; her cable network does not promise to be nearly as effective in this regard.

Twenty-five years is a good run for any television personality, and Oprah Winfrey has certainly achieved a place in the history of American popular culture, but on Thursday, the day after her final show airs, the sun will rise and the sun will set. Life will go on, even without “Oprah,” but we may find ourselves thinking about her whenever our jeans aren’t fitting or our dreams aren’t working; whenever it seems that it might, at last, be time to make a change.

Robert J. Thompson is the founding director of the Bleier Center for Television and Popular Culture at Syracuse University, where he is also a Trustee Professor of Television and Popular Culture at the S.I. Newhouse School of Public Communications. He was a visiting professor for six summers at Cornell University and served for nine years as professor and director of the N.H.S.I. Television and Film Institute at Northwestern University.

Robert Thompson is founding director of the Bleier Center for Television and Popular Culture at Syracuse University and a trustee professor.