The original moderators were Ben Webster, David Zureick-Brown, Dan Erman, and Scott Morrison. François and I were elected in June 2010. See tea.mathoverflow.net/discussion/426/2/…
@S.Carnahan Wasn't Anton Geraschenko on e of the original moderators, too?
Or should he be described as site administrator?
On September 28, I finally got into the SE beta. I set up the site, deputized moderators Dave Brown, Dan Erman, and Scott Morrison... from What's the story behind mathoverflow?