| | Plainfield, IL | Brentwood, TN | United States |
| Population | 44,296 | 44,354 | 329,725,481 |
| Female Population | 50.7% | 49.1% | 50.5% |
| Male Population | 49.4% | 50.9% | 49.5% |
| Median Age | 37.3 | 43.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 39,990 | 37,211 | 309,327,143 |
| Population - 2000 | 13,038 | 23,445 | 285,036,114 |
| Population - 1990 | 4,557 | 16,392 | 251,960,433 |
| Pop. 2000 to Now | 241.6% | 82.9% | 15.6% |
| Pop. 1990 to Now | 877.4% | 161.6% | 30.8% |
| space4 | | | |
| Population Density | 1,808.1 | 1,079.2 | 93.4 |
| Land Area | 24.5 | 41.1 | 3,531,905.4 |
| Water Area | 1.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Plainfield, IL | Brentwood, TN | United States |
| Age 0 to 4 | 5.7% | 3.7% | 5.9% |
| Age 5 to 9 | 8.2% | 7.0% | 6.1% |
| Age 10 to 14 | 10.5% | 9.4% | 6.6% |
| Age 15 to 17 | 5.8% | 8.6% | 3.9% |
| Age 18 to 20 | 3.8% | 3.5% | 4.0% |
| Age 21 to 24 | 4.3% | 3.7% | 5.2% |
| Age 25 to 34 | 8.7% | 5.1% | 13.8% |
| Age 35 to 44 | 15.6% | 12.1% | 12.9% |
| Age 45 to 54 | 17.9% | 18.3% | 12.6% |
| Age 55 to 59 | 6.0% | 7.3% | 6.7% |
| Age 60 to 64 | 4.3% | 7.1% | 6.3% |
| Age 65 to 74 | 5.6% | 8.8% | 9.6% |
| Age 75 to 84 | 2.4% | 4.2% | 4.5% |
| Age 85 and over | 1.3% | 1.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | Plainfield, IL | Brentwood, TN | United States |
| White | 68.6% | 83.6% | 59.4% |
| Black | 8.3% | 3.1% | 12.2% |
| Asian | 9.4% | 7.7% | 5.6% |
| Native American | 0.2% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.0% | 0.2% |
| Other | 0.3% | 0.1% | 0.4% |
| Two or More Races | 3.3% | 2.0% | 3.2% |
| Hispanic | 9.9% | 3.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Plainfield, IL | Brentwood, TN | United States |
| Married Population | 62.9% | 66.6% | 49.8% |
| Currently Married | 62.1% | 66.2% | 48.0% |
| Married but Separated | 0.8% | 0.4% | 1.8% |
| Single Population | 37.1% | 33.4% | 50.2% |
| Never Married | 27.5% | 23.8% | 33.8% |
| Divorced | 6.5% | 6.1% | 10.8% |
| Widowed | 3.2% | 3.5% | 5.6% |
| space5 | | | |
| Household Size | 3.27 | 3.04 | 2.60 |
| Households | 13,510 | 14,550 | 124,010,992 |
| Family Households | 11,525 | 12,315 | 80,755,759 |
| Married couple, w/children | 50.1% | 44.6% | 30.5% |
| Married couple, no children | 34.6% | 46.3% | 42.9% |
| Non Family Households | 1,985 | 2,235 | 43,255,233 |
| Single householder, w/children | 9.3% | 5.3% | 15.8% |
| Single householder, no children | 6.0% | 3.7% | 10.8% |