| | Lockport, IL | Alton, IL | United States |
| Population | 26,070 | 25,902 | 329,725,481 |
| Female Population | 51.4% | 52.2% | 50.5% |
| Male Population | 48.6% | 47.8% | 49.5% |
| Median Age | 36.8 | 38.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 24,919 | 27,901 | 309,327,143 |
| Population - 2000 | 15,191 | 30,496 | 285,036,114 |
| Population - 1990 | 9,401 | 32,905 | 251,960,433 |
| Pop. 2000 to Now | 70.4% | -14.6% | 15.6% |
| Pop. 1990 to Now | 175.4% | -20.8% | 30.8% |
| space4 | | | |
| Population Density | 2,285.6 | 1,669.5 | 93.4 |
| Land Area | 11.4 | 15.5 | 3,531,905.4 |
| Water Area | 0.0 | 1.3 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Lockport, IL | Alton, IL | United States |
| Age 0 to 4 | 6.0% | 5.5% | 5.9% |
| Age 5 to 9 | 6.5% | 7.9% | 6.1% |
| Age 10 to 14 | 8.5% | 7.2% | 6.6% |
| Age 15 to 17 | 6.3% | 3.6% | 3.9% |
| Age 18 to 20 | 3.6% | 3.5% | 4.0% |
| Age 21 to 24 | 4.0% | 3.0% | 5.2% |
| Age 25 to 34 | 13.2% | 14.5% | 13.8% |
| Age 35 to 44 | 13.9% | 13.5% | 12.9% |
| Age 45 to 54 | 15.7% | 11.7% | 12.6% |
| Age 55 to 59 | 7.0% | 6.0% | 6.7% |
| Age 60 to 64 | 4.3% | 7.3% | 6.3% |
| Age 65 to 74 | 7.4% | 10.4% | 9.6% |
| Age 75 to 84 | 2.9% | 4.4% | 4.5% |
| Age 85 and over | 0.7% | 1.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | Lockport, IL | Alton, IL | United States |
| White | 84.1% | 67.1% | 59.4% |
| Black | 2.1% | 25.1% | 12.2% |
| Asian | 1.6% | 0.6% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 2.4% | 5.0% | 3.2% |
| Hispanic | 9.9% | 1.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Lockport, IL | Alton, IL | United States |
| Married Population | 53.7% | 36.6% | 49.8% |
| Currently Married | 53.1% | 33.8% | 48.0% |
| Married but Separated | 0.6% | 2.8% | 1.8% |
| Single Population | 46.3% | 63.4% | 50.2% |
| Never Married | 30.2% | 37.6% | 33.8% |
| Divorced | 11.2% | 17.2% | 10.8% |
| Widowed | 4.9% | 8.7% | 5.6% |
| space5 | | | |
| Household Size | 2.83 | 2.29 | 2.60 |
| Households | 9,139 | 11,097 | 124,010,992 |
| Family Households | 6,810 | 5,853 | 80,755,759 |
| Married couple, w/children | 38.3% | 23.2% | 30.5% |
| Married couple, no children | 39.7% | 32.2% | 42.9% |
| Non Family Households | 2,329 | 5,244 | 43,255,233 |
| Single householder, w/children | 12.2% | 31.4% | 15.8% |
| Single householder, no children | 9.8% | 13.3% | 10.8% |