Found this as well:
William Sydney Porter
Porter was born on September 11, 1862, in Greensboro, North Carolina. His middle name at birth was Sidney; he changed the spelling in 1898. His parents were Dr. Algernon Sidney Porter (1825–1888) and Mary Jane Virginia Swain Porter (1833–1865). They were married April 20, 1858. When William was three, his mother died from tuberculosis, and he and his father moved into the home of his paternal grandmother.
Here is a source for that information: