| | West Allis, WI | Muskego, WI | United States |
| Population | 60,220 | 24,991 | 329,725,481 |
| Female Population | 50.8% | 48.7% | 50.5% |
| Male Population | 49.2% | 51.3% | 49.5% |
| Median Age | 38.2 | 43.5 | 38.4 |
| space3 | | | |
| Population - 2010 | 60,404 | 24,155 | 309,327,143 |
| Population - 2000 | 61,254 | 21,397 | 285,036,114 |
| Population - 1990 | 63,221 | 16,813 | 251,960,433 |
| Pop. 2000 to Now | -2.5% | 18.3% | 15.6% |
| Pop. 1990 to Now | -5.5% | 50.6% | 30.8% |
| space4 | | | |
| Population Density | 5,291.3 | 790.8 | 93.4 |
| Land Area | 11.4 | 31.6 | 3,531,905.4 |
| Water Area | 0.0 | 4.4 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | West Allis, WI | Muskego, WI | United States |
| Age 0 to 4 | 6.1% | 4.6% | 5.9% |
| Age 5 to 9 | 5.6% | 6.1% | 6.1% |
| Age 10 to 14 | 4.8% | 7.2% | 6.6% |
| Age 15 to 17 | 3.3% | 5.2% | 3.9% |
| Age 18 to 20 | 2.1% | 2.9% | 4.0% |
| Age 21 to 24 | 3.8% | 4.5% | 5.2% |
| Age 25 to 34 | 18.9% | 7.1% | 13.8% |
| Age 35 to 44 | 13.7% | 14.0% | 12.9% |
| Age 45 to 54 | 11.6% | 15.2% | 12.6% |
| Age 55 to 59 | 6.7% | 8.9% | 6.7% |
| Age 60 to 64 | 7.7% | 7.1% | 6.3% |
| Age 65 to 74 | 10.1% | 11.4% | 9.6% |
| Age 75 to 84 | 3.2% | 4.1% | 4.5% |
| Age 85 and over | 2.5% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | West Allis, WI | Muskego, WI | United States |
| White | 70.9% | 93.4% | 59.4% |
| Black | 6.2% | 0.6% | 12.2% |
| Asian | 3.1% | 0.9% | 5.6% |
| Native American | 0.5% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.3% | 0.1% | 0.4% |
| Two or More Races | 4.2% | 1.5% | 3.2% |
| Hispanic | 14.7% | 3.3% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | West Allis, WI | Muskego, WI | United States |
| Married Population | 39.9% | 63.3% | 49.8% |
| Currently Married | 38.7% | 63.2% | 48.0% |
| Married but Separated | 1.2% | 0.1% | 1.8% |
| Single Population | 60.1% | 36.7% | 50.2% |
| Never Married | 39.3% | 22.8% | 33.8% |
| Divorced | 14.8% | 8.0% | 10.8% |
| Widowed | 6.0% | 5.9% | 5.6% |
| space5 | | | |
| Household Size | 2.14 | 2.59 | 2.60 |
| Households | 27,808 | 9,600 | 124,010,992 |
| Family Households | 13,644 | 7,314 | 80,755,759 |
| Married couple, w/children | 24.6% | 34.4% | 30.5% |
| Married couple, no children | 43.3% | 53.0% | 42.9% |
| Non Family Households | 14,164 | 2,286 | 43,255,233 |
| Single householder, w/children | 20.0% | 6.7% | 15.8% |
| Single householder, no children | 12.0% | 5.9% | 10.8% |