| | Lemont, IL | Plainfield, IL | United States |
| Population | 17,535 | 44,296 | 329,725,481 |
| Female Population | 49.3% | 50.7% | 50.5% |
| Male Population | 50.7% | 49.4% | 49.5% |
| Median Age | 44 | 37.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 16,075 | 39,990 | 309,327,143 |
| Population - 2000 | 13,098 | 13,038 | 285,036,114 |
| Population - 1990 | 7,348 | 4,557 | 251,960,433 |
| Pop. 2000 to Now | 32.4% | 241.6% | 15.6% |
| Pop. 1990 to Now | 136.0% | 877.4% | 30.8% |
| space4 | | | |
| Population Density | 2,167.5 | 1,808.1 | 93.4 |
| Land Area | 8.1 | 24.5 | 3,531,905.4 |
| Water Area | 0.4 | 1.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Lemont, IL | Plainfield, IL | United States |
| Age 0 to 4 | 4.0% | 5.7% | 5.9% |
| Age 5 to 9 | 8.6% | 8.2% | 6.1% |
| Age 10 to 14 | 7.5% | 10.5% | 6.6% |
| Age 15 to 17 | 4.7% | 5.8% | 3.9% |
| Age 18 to 20 | 3.2% | 3.8% | 4.0% |
| Age 21 to 24 | 3.6% | 4.3% | 5.2% |
| Age 25 to 34 | 7.4% | 8.7% | 13.8% |
| Age 35 to 44 | 12.7% | 15.6% | 12.9% |
| Age 45 to 54 | 13.9% | 17.9% | 12.6% |
| Age 55 to 59 | 8.9% | 6.0% | 6.7% |
| Age 60 to 64 | 6.4% | 4.3% | 6.3% |
| Age 65 to 74 | 9.1% | 5.6% | 9.6% |
| Age 75 to 84 | 6.2% | 2.4% | 4.5% |
| Age 85 and over | 3.7% | 1.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Lemont, IL | Plainfield, IL | United States |
| White | 89.1% | 68.6% | 59.4% |
| Black | 0.5% | 8.3% | 12.2% |
| Asian | 2.0% | 9.4% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 1.4% | 3.3% | 3.2% |
| Hispanic | 7.0% | 9.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Lemont, IL | Plainfield, IL | United States |
| Married Population | 61.6% | 62.9% | 49.8% |
| Currently Married | 60.7% | 62.1% | 48.0% |
| Married but Separated | 0.9% | 0.8% | 1.8% |
| Single Population | 38.4% | 37.1% | 50.2% |
| Never Married | 24.8% | 27.5% | 33.8% |
| Divorced | 7.5% | 6.5% | 10.8% |
| Widowed | 6.2% | 3.2% | 5.6% |
| space5 | | | |
| Household Size | 2.83 | 3.27 | 2.60 |
| Households | 6,119 | 13,510 | 124,010,992 |
| Family Households | 4,736 | 11,525 | 80,755,759 |
| Married couple, w/children | 40.0% | 50.1% | 30.5% |
| Married couple, no children | 46.0% | 34.6% | 42.9% |
| Non Family Households | 1,383 | 1,985 | 43,255,233 |
| Single householder, w/children | 8.7% | 9.3% | 15.8% |
| Single householder, no children | 5.3% | 6.0% | 10.8% |