| | St. Andrews, SC | Lexington, SC | United States |
| Population | 21,383 | 23,068 | 329,725,481 |
| Female Population | 53.4% | 50.4% | 50.5% |
| Male Population | 46.7% | 49.6% | 49.5% |
| Median Age | 32.5 | 37.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 20,835 | 18,714 | 309,327,143 |
| Population - 2000 | 21,814 | 9,793 | 285,036,114 |
| Population - 1990 | 25,692 | 3,289 | 251,960,433 |
| Pop. 2000 to Now | 3.9% | 132.0% | 15.6% |
| Pop. 1990 to Now | -11.8% | 590.7% | 30.8% |
| space4 | | | |
| Population Density | 3,452.8 | 2,020.9 | 93.4 |
| Land Area | 6.2 | 11.4 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | St. Andrews, SC | Lexington, SC | United States |
| Age 0 to 4 | 6.9% | 7.7% | 5.9% |
| Age 5 to 9 | 6.2% | 7.0% | 6.1% |
| Age 10 to 14 | 4.9% | 6.5% | 6.6% |
| Age 15 to 17 | 2.6% | 3.4% | 3.9% |
| Age 18 to 20 | 3.9% | 3.1% | 4.0% |
| Age 21 to 24 | 8.9% | 3.3% | 5.2% |
| Age 25 to 34 | 20.1% | 14.9% | 13.8% |
| Age 35 to 44 | 13.7% | 17.2% | 12.9% |
| Age 45 to 54 | 10.5% | 11.2% | 12.6% |
| Age 55 to 59 | 6.1% | 5.7% | 6.7% |
| Age 60 to 64 | 4.6% | 6.0% | 6.3% |
| Age 65 to 74 | 7.7% | 6.6% | 9.6% |
| Age 75 to 84 | 2.7% | 4.5% | 4.5% |
| Age 85 and over | 1.1% | 2.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | St. Andrews, SC | Lexington, SC | United States |
| White | 22.1% | 76.1% | 59.4% |
| Black | 66.5% | 10.5% | 12.2% |
| Asian | 2.1% | 5.3% | 5.6% |
| Native American | 0.1% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.7% | 0.2% |
| Other | 0.6% | 0.0% | 0.4% |
| Two or More Races | 4.6% | 2.0% | 3.2% |
| Hispanic | 4.1% | 5.3% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | St. Andrews, SC | Lexington, SC | United States |
| Married Population | 31.0% | 54.5% | 49.8% |
| Currently Married | 27.2% | 52.1% | 48.0% |
| Married but Separated | 3.8% | 2.3% | 1.8% |
| Single Population | 69.0% | 45.5% | 50.2% |
| Never Married | 49.2% | 28.2% | 33.8% |
| Divorced | 15.3% | 11.5% | 10.8% |
| Widowed | 4.5% | 5.8% | 5.6% |
| space5 | | | |
| Household Size | 2.10 | 2.44 | 2.60 |
| Households | 10,111 | 8,923 | 124,010,992 |
| Family Households | 4,746 | 5,565 | 80,755,759 |
| Married couple, w/children | 21.5% | 43.0% | 30.5% |
| Married couple, no children | 26.3% | 36.6% | 42.9% |
| Non Family Households | 5,365 | 3,358 | 43,255,233 |
| Single householder, w/children | 32.7% | 15.8% | 15.8% |
| Single householder, no children | 19.5% | 4.7% | 10.8% |