Who was "O. Henry" ? [not the candy bar]

from Writer's Almanac dot-org (American Public Media: Garrison Keillor):
September 11 is the birthday of William Sydney Porter, better known as O. Henry, born in Greensboro, North Carolina (1862). He's the author of the beloved short stories "The Gift of the Magi" and "The Ransom of Red Chief," and he became a writer while serving time in a federal prison for embezzlement. He was sentenced to five years, but was let out after three for good behavior; during his incarceration he published 14 stories, and wrote about 400 more upon his release.
Henry said: "You can't write a story that's got any life in it by sitting at a writing table and thinking. You've got to get out into the streets, into the crowds, talk with people, and feel the rush and throb of real life — that's the stimulant for a story writer."