Fortune's writeup from 1998: Oprah's power is her influence -- over the entertainment industry, the book-publishing business, mass culture. Via her syndicated TV show, she reaches 33 million people weekly in the U.S., plus millions more in 135 international markets. Via deals with Disney, she produces socially conscious TV movies and feature films. Via Oprah's Book Club, she drives the market for serious fiction.
This year's Most Powerful Women are shaping the future of technology, defense, and media.