Founded in 1839, Marshall County is one of 102 counties in the state of Illinois. Historically, Marshall County was formed from Putnam County. The city of Lacon is the county seat. With FIPS code of 123, Marshall County has a population of 11,663 and area of 386 square miles (1,000 km2).
List of all cities in Marshall County, IL alphabetically
| City/Town | Postal Code | Area Code |
| Bell Plain, IL | 61541 | 309 |
| Camp Grove, IL | 61424 | 309 |
| East Wenona, IL | 61377 | 815/779 |
| Evans, IL | 61377 | 815/779 |
| Garfield, IL | 61377 | 815/779 |
| Henry, IL | 61537 | 309 |
| Hopewell, IL | 61565 | 309 |
| Hopewell Estates, IL | 61565 | 309 |
| La Rose, IL | 61541 | 309 |
| Lacon, IL | 61540 | 309 |
| Leeds, IL | 61377 | 815/779 |
| Pattonsburg, IL | 61369 | 815/779 |
| Saratoga Center, IL | 61537 | 309 |
| Sparland, IL | 61565 | 309 |
| Toluca, IL | 61369 | 815/779 |
| Varna, IL | 61375 | 309 |
| Washburn, IL | 61570 | 309 |
| Wenona, IL | 61377 | 815/779 |
| Wilbern, IL | 61570 | 309 |