| | Sidney, IL | Bethalto, IL | United States |
| Population | 1,040 | 9,414 | 329,725,481 |
| Female Population | 50.9% | 52.9% | 50.5% |
| Male Population | 49.1% | 47.1% | 49.5% |
| Median Age | 36.6 | 41.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,247 | 9,515 | 309,327,143 |
| Population - 2000 | 1,062 | 9,454 | 285,036,114 |
| Population - 1990 | 1,027 | 9,507 | 251,960,433 |
| Pop. 2000 to Now | 10.4% | -2.7% | 15.6% |
| Pop. 1990 to Now | 14.1% | -3.2% | 30.8% |
| space4 | | | |
| Population Density | 1,666.7 | 1,254.4 | 93.4 |
| Land Area | 0.6 | 7.5 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Sidney, IL | Bethalto, IL | United States |
| Age 0 to 4 | 8.9% | 5.2% | 5.9% |
| Age 5 to 9 | 7.7% | 6.5% | 6.1% |
| Age 10 to 14 | 6.9% | 6.6% | 6.6% |
| Age 15 to 17 | 3.1% | 4.7% | 3.9% |
| Age 18 to 20 | 1.1% | 1.6% | 4.0% |
| Age 21 to 24 | 5.2% | 2.7% | 5.2% |
| Age 25 to 34 | 14.1% | 15.3% | 13.8% |
| Age 35 to 44 | 12.4% | 13.1% | 12.9% |
| Age 45 to 54 | 12.9% | 10.7% | 12.6% |
| Age 55 to 59 | 5.5% | 6.4% | 6.7% |
| Age 60 to 64 | 6.6% | 5.8% | 6.3% |
| Age 65 to 74 | 8.1% | 8.9% | 9.6% |
| Age 75 to 84 | 5.7% | 10.3% | 4.5% |
| Age 85 and over | 1.8% | 2.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | Sidney, IL | Bethalto, IL | United States |
| White | 95.4% | 94.6% | 59.4% |
| Black | 0.8% | 1.4% | 12.2% |
| Asian | 0.3% | 0.1% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 2.3% | 2.1% | 3.2% |
| Hispanic | 1.3% | 1.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Sidney, IL | Bethalto, IL | United States |
| Married Population | 61.1% | 55.3% | 49.8% |
| Currently Married | 60.8% | 54.7% | 48.0% |
| Married but Separated | 0.4% | 0.7% | 1.8% |
| Single Population | 38.9% | 44.7% | 50.2% |
| Never Married | 24.2% | 23.7% | 33.8% |
| Divorced | 9.6% | 14.7% | 10.8% |
| Widowed | 5.2% | 6.3% | 5.6% |
| space5 | | | |
| Household Size | 2.51 | 2.34 | 2.60 |
| Households | 414 | 3,987 | 124,010,992 |
| Family Households | 289 | 2,594 | 80,755,759 |
| Married couple, w/children | 29.4% | 36.2% | 30.5% |
| Married couple, no children | 48.8% | 42.5% | 42.9% |
| Non Family Households | 125 | 1,393 | 43,255,233 |
| Single householder, w/children | 14.9% | 14.3% | 15.8% |
| Single householder, no children | 6.9% | 7.0% | 10.8% |