| Place Name | Johnstown (Rock County) |
| Place Type | Town |
| County | Rock County |
| Area Code(s) | 608 |
| Timezone | Central Daylight Time (CDT) |
| Population (2021) | 735 |
| Majority Ethnicity | White 96.4% |
| Metro/Micro Stats Area | Janesville-Beloit, WI |
| US Congressional District(s) | Wisconsin 1st |
| State Assembly Districts | 31 |
| State Senate Districts | 11 |
| Race/Ethnicy | Percentage of Population (2021) |
|---|---|
| White | 96.4% |
| African American | 0.55% |
| Hispanic | 0% |
| Asian | 0% |
| Native American | 0% |
| Hawaiin/Pacific Islander | 3.05% |