(This is an addendum to James Gunn's review of The Ultimate Egoist : Volume 1 The Complete Stories of Theododore Sturgeon which originally appeared in The New York Review of Science Fiction #85, September 1995, and is reproduced here with the author's permission)
Sturgeon's Law was first laid down at a session of the World Science Fiction Covention in Philadelphia, held over the Labor Day weekend of 1953. It was my second convention, so it remains fresh in my memory. Many of the writers and editors that I hadn't met in Chicago, the year before, I met there: Randall Garrett, Bob Sheckley, Bob Silverberg, Harlan Ellison, Philip Jose Farmer, Ted Cogswell (who arrived on his motorcycle), all the young Turks, and some of the older ones such as Isaac Asimov, L. Sprague de Camp, and Willy Ley (whom I had at least seen in Chicago), and others whom I may have forgotten or overlooked. And Ted Sturgeon, who had brought along his 12-stringed guitar and sang Strange Fruit upon one occasion.
Of course what became known as Sturgeon's Law was then only a sentence in a talk that Ted gave to the entire convention; total membership was only 750, and there was no need for separate programming. The general thrust of Ted's remarks was that science fiction was the only genre that was evaluated by its worst examples rather than its best. "When people talk about the mystery novel," Ted said, as I remember, "they mention The Maltese Falcon and The Big Sleep. When they talk about the western, they say there's The Way West and Shane. But when they talk about science fiction, they call it 'that Buck Rogers stuff,' and they say 'ninety percent of science fiction is crud.' Well, they're right. Ninety percent of science fiction is crud. But then ninety percent of everything is crud, and it's the ten percent that isn't crud that is important. and the ten percent of science fiction that isn't crud is as good as or better than anything being written anywhere."
©James Gunn 1995
See also additional information here, in the Theodore Sturgeon FAQ.