| | Middlesex, NC | Clayton, NC | United States |
| Population | 1,141 | 25,486 | 329,725,481 |
| Female Population | 52.7% | 51.2% | 50.5% |
| Male Population | 47.3% | 48.8% | 49.5% |
| Median Age | 34 | 33.9 | 38.4 |
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| Population - 2010 | 829 | 16,307 | 309,327,143 |
| Population - 2000 | 838 | 6,973 | 285,036,114 |
| Population - 1990 | 730 | 4,756 | 251,960,433 |
| Pop. 2000 to Now | -0.5% | 279.4% | 15.6% |
| Pop. 1990 to Now | 14.3% | 456.3% | 30.8% |
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| Population Density | 1,091.9 | 1,706.5 | 93.4 |
| Land Area | 1.0 | 14.9 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Middlesex, NC | Clayton, NC | United States |
| Age 0 to 4 | 8.2% | 5.8% | 5.9% |
| Age 5 to 9 | 6.7% | 7.8% | 6.1% |
| Age 10 to 14 | 5.1% | 7.9% | 6.6% |
| Age 15 to 17 | 9.2% | 5.3% | 3.9% |
| Age 18 to 20 | 4.0% | 2.4% | 4.0% |
| Age 21 to 24 | 4.8% | 6.6% | 5.2% |
| Age 25 to 34 | 14.4% | 15.2% | 13.8% |
| Age 35 to 44 | 10.3% | 13.1% | 12.9% |
| Age 45 to 54 | 15.7% | 13.9% | 12.6% |
| Age 55 to 59 | 9.0% | 6.6% | 6.7% |
| Age 60 to 64 | 2.5% | 4.7% | 6.3% |
| Age 65 to 74 | 6.6% | 5.8% | 9.6% |
| Age 75 to 84 | 2.8% | 4.0% | 4.5% |
| Age 85 and over | 0.7% | 0.9% | 1.9% |
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| Race | | | |
| | Middlesex, NC | Clayton, NC | United States |
| White | 55.5% | 59.3% | 59.4% |
| Black | 30.6% | 22.4% | 12.2% |
| Asian | 0.0% | 1.0% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 1.6% | 0.4% |
| Two or More Races | 2.0% | 2.5% | 3.2% |
| Hispanic | 11.9% | 13.2% | 18.4% |
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| Marriage & Family | | | |
| | Middlesex, NC | Clayton, NC | United States |
| Married Population | 34.0% | 51.0% | 49.8% |
| Currently Married | 30.0% | 48.4% | 48.0% |
| Married but Separated | 3.9% | 2.6% | 1.8% |
| Single Population | 66.0% | 49.0% | 50.2% |
| Never Married | 38.1% | 31.9% | 33.8% |
| Divorced | 17.0% | 13.0% | 10.8% |
| Widowed | 11.0% | 4.1% | 5.6% |
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| Household Size | 2.44 | 2.79 | 2.60 |
| Households | 467 | 9,090 | 124,010,992 |
| Family Households | 291 | 6,435 | 80,755,759 |
| Married couple, w/children | 15.1% | 35.3% | 30.5% |
| Married couple, no children | 25.1% | 35.7% | 42.9% |
| Non Family Households | 176 | 2,655 | 43,255,233 |
| Single householder, w/children | 47.1% | 21.6% | 15.8% |
| Single householder, no children | 12.7% | 7.4% | 10.8% |