Folsom was an American city in California.
Gabriel Panatello was incarcerated in Folsom for a time. After being released, Panatello occasionally found work for his fellow prisoners, including Doogie, through his illicit messenger service.
While running a search on the name "Kyle Risdow," CTU analyst Jamey Farrell found six people by that name from the Los Angeles area, one of whom was incarcerated at a prison in Folsom. (Chaos Theory)