Ben took the name Henry Gale from the balloon guy that got killed, who was from Kansas. (Wizard of Oz, Dorthy's dad)
Which is neat, as Locke calls him the man behind the curtain, which is a Wizard of Oz reference again.
But his real last name is unknown at this point, it's just Ben. I thought it was Workman for awhile, but that was just the title of his dad on the shirt. Like janitor.