Jimmy's history is unknown. What is known is that he worked for the US government, running secret missions that were hidden from the rest of the world. He worked with the other adventurers from that time, including Axel Brass and the Spider.
He is based on the archetype of the secret agent akin to Operator 5, James Bond and in some ways The Spirit.
Jimmy died in the group's Adirondack headquarters in 1945, saving the world from invaders from an alternate Earth.