Dear Ms. Pearce,
Thank you for posting your request on History Hub!
The Illinois State Archives website provides numerous sources for state-related research, such as the Illinois Regional Archives Depository (IRAD) System. We suggest reviewing the information available and contacting the appropriate office for assistance.
The Office of the Illinois Secretary of State has an online pamphlet titled Origin and Evolution of Illinois Counties that includes information about Franklin County and numerous maps from early Illinois history.
We hope this is helpful. Best of luck with your research!