Born William Sydney Porter, he is the oldest famous resident of Austin I know of because all the founders of the state lived elsewhere. Most people know him from high school literature with all his short stories ending in a twist, namely Gift of the Magi and The Ransom of Red Chief. I like to think of him as an abbreviated Mark Twain with maybe a “lower” sense of humor.
If you ever come to Austin, there is an actual museum dedicated to him and his works down on Fifth Street. I readily admit that I’ve never been to it nor have I ever attended the annual O. Henry Pun-Off World Championship held in May. The latter matter I’m sure just elicits hundreds of groan.