Founded in 1841, Piatt County is one of 102 counties in the state of Illinois. Historically, Piatt County was formed from DeWitt and Macon County. The city of Monticello is the county seat. With FIPS code of 147, Piatt County has a population of 16,753 and area of 439 square miles (1,137 km2).
List of all cities in Piatt County, IL alphabetically
| City/Town | Postal Code | Area Code |
| Bement, IL | 61813 | 217 |
| Cerro Gordo, IL | 61818 | 217 |
| Cisco, IL | 61830 | 217 |
| De Land, IL | 61839 | 217 |
| Hammond, IL | 61929 | 217 |
| La Place, IL | 61936 | 217 |
| Lodge, IL | 61856 | 217 |
| Mansfield, IL | 61854 | 217 |
| Milmine, IL | 61855 | 217 |
| Monticello, IL | 61856 | 217 |
| Pierson Station, IL | 61929 | 217 |
| White Heath, IL | 61884 | 217 |