
Piatt County
- State:
- Illinois
- County Seat:
- Monticello
Piatt County's estimated 2025 population is 16,792 with a growth rate of 0.23% in the past year according to the most recent United States census data. Piatt County is the 61st largest county in Illinois. The 2010 population was 16,710 and has seen a growth of 0.49% since that time.