Waterloo city, Illinois
Official LSAD Designation: Waterloo city • Census GEOID: 1779150
• Monroe County
Demographics & Population Profile
Population and demographics for Waterloo city.
| Demographic Variable | Estimate / Count | Margin of Error | Period | Source |
|---|---|---|---|---|
| Total Population (2025 PEP Estimate) | 11,132 | — | 2025 | Census |
| Median Age | 41.5 yrs | ±2.6 | 2020-2024 | Census ACS 5-Year 2024 |
| Total Households | 4,491 | ±227 | 2020-2024 | Census ACS 5-Year 2024 |
Source: U.S. Census Bureau (PEP, ACS 5-Year).