Excerpt from the transcript of the meeting in which George Lucas, Steven Spielberg, and Lawrence Kasdan conceived Raiders of the Lost Ark (extensive highlights here, full text PDF here):

Kasdan — Do you have a name for this person?

Lucas — I do for our leader.

Spielberg — I hate this, but go ahead.

Lucas — Indiana Smith. It has to be unique. It’s a character. Very Americana square. He was born in Indiana.

Via BoingBoing.