Iowa was the U.S. state from which members of Habib Marwan's terrorist cell launched a nuclear strike.
Day 4
Morrison launches Marwan's nuclear missile from Iowa
Robert Morrison and Sabir Ardakani, terrorists funded by Habib Marwan, launched a nuclear weapon at Los Angeles from a remote area in Iowa. The staff of CTU Los Angeles was able to view the rocket setup live from a feed found on Yassir's computer, but were helpless to stop the launch. The missile was intercepted over Los Angeles shortly after its launch.
Background information and notes
Although the terrorists are supposedly in the mountains of Iowa, there are no mountains anywhere in Iowa. There are, however, low rugged hill areas located throughout the state.