| Harrisonville, Illinois | |
| Settlement Type: | Unincorporated community |
| Etymology: | William Henry Harrison |
| Subdivision Type: | Country |
| Subdivision Name: | United States |
| Subdivision Type1: | State |
| Subdivision Name1: | Illinois |
| Subdivision Type2: | County |
| Subdivision Name2: | Monroe |
| Subdivision Type3: | Precinct |
| Subdivision Name3: | 15 |
| Pushpin Map: | Illinois#USA |
| Pushpin Label: | Harrisonville |
| Coordinates: | 38.2775°N -90.35°W |
| Elevation Ft: | 397 |
| Population Density Km2: | auto |
| Timezone1: | CST |
| Utc Offset1: | -6 |
| Timezone1 Dst: | CDT |
| Utc Offset1 Dst: | -5 |
| Postal Code Type: | Postal code |
| Postal Code: | 62295 |
| Area Code: | 618 |
Harrisonville is an unincorporated community in the historic Harrisonville Precinct of Monroe County, Illinois.
Harrisonville was the first county seat of Monroe County, and was originally called Carthage, or even earlier, in 1786, as Brashear's Fort. The name was changed by an act of the territorial assembly, in 1816, to honor William Henry Harrison, who actually owned several tracts of land in the area, mostly in Moredock precinct. However, sources suggest the name was already in common usage by 1810 or even earlier. The original site, some distance west of its current location has been swallowed up by the Mississippi River, and was obliterated by 1860. It was an important shipping point on the Mississippi River, lying on the bank directly opposite Herculaneum, Missouri and drawing on the agricultural production of the American Bottom.[1]