Twenty-one-year-old Lance Corporal Jakub H. Kowalik of Schaumburg died Monday.
The Defense Department says he was killed when ordnance he was handling exploded.
State Representative Paul Froelich of Schaumburg says Kowalik made the ultimate sacrifice for his country.
Kowalik was the first of two Illinois Marines killed in Iraq this week.
Nineteen-year-old Lance Corporal Nicholas Brian Kleiboeker of Odin in southern Illinois died Tuesday when the bunker he was working in caught fire and exploded.
Officials say both incidents are under investigation.