Born in Chicago, James Underdown grew up in Wheaton, IL, a few blocks from the Belushis, and attended grade school through high school with Bill Belushi, the youngest Belushi brother.

After attending Wheaton Central High School, College of DuPage, and DePauw University (and playing for each institution's football teams), Underdown lived in Los Angeles during the early 1980s and was an extra in film and TV.

In the late 80s, after graduating from the Players Workshop of the Second City, Underdown began a 5 year career as a stand-up comic, billing himself as Jim U-Boat, Poet Laureate of Calumet City, IL. He moved back to Los Angeles in the 90s and eventually was hired by the Center for Inquiry, where he became and remains executive director.