| | Peru, IL | Casper, WY | United States |
| Population | 9,862 | 58,547 | 329,725,481 |
| Female Population | 53.0% | 49.8% | 50.5% |
| Male Population | 47.0% | 50.2% | 49.5% |
| Median Age | 47.4 | 36.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 10,320 | 55,261 | 309,327,143 |
| Population - 2000 | 9,835 | 49,644 | 285,036,114 |
| Population - 1990 | 9,302 | 46,742 | 251,960,433 |
| Pop. 2000 to Now | -2.3% | 17.8% | 15.6% |
| Pop. 1990 to Now | 3.3% | 25.2% | 30.8% |
| space4 | | | |
| Population Density | 1,043.5 | 2,206.7 | 93.4 |
| Land Area | 9.5 | 26.5 | 3,531,905.4 |
| Water Area | 0.1 | 0.3 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Peru, IL | Casper, WY | United States |
| Age 0 to 4 | 5.8% | 6.9% | 5.9% |
| Age 5 to 9 | 6.9% | 6.3% | 6.1% |
| Age 10 to 14 | 5.2% | 6.9% | 6.6% |
| Age 15 to 17 | 3.2% | 4.1% | 3.9% |
| Age 18 to 20 | 1.8% | 3.7% | 4.0% |
| Age 21 to 24 | 3.6% | 4.6% | 5.2% |
| Age 25 to 34 | 11.9% | 14.9% | 13.8% |
| Age 35 to 44 | 10.1% | 13.7% | 12.9% |
| Age 45 to 54 | 11.4% | 11.2% | 12.6% |
| Age 55 to 59 | 9.4% | 6.0% | 6.7% |
| Age 60 to 64 | 6.4% | 6.2% | 6.3% |
| Age 65 to 74 | 11.8% | 9.2% | 9.6% |
| Age 75 to 84 | 7.2% | 4.3% | 4.5% |
| Age 85 and over | 5.4% | 2.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Peru, IL | Casper, WY | United States |
| White | 88.9% | 86.4% | 59.4% |
| Black | 1.2% | 0.7% | 12.2% |
| Asian | 0.9% | 0.4% | 5.6% |
| Native American | 0.0% | 1.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 1.9% | 2.9% | 3.2% |
| Hispanic | 7.1% | 8.5% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Peru, IL | Casper, WY | United States |
| Married Population | 53.9% | 48.9% | 49.8% |
| Currently Married | 53.2% | 48.0% | 48.0% |
| Married but Separated | 0.7% | 0.9% | 1.8% |
| Single Population | 46.1% | 51.1% | 50.2% |
| Never Married | 24.4% | 30.1% | 33.8% |
| Divorced | 10.8% | 15.1% | 10.8% |
| Widowed | 10.9% | 5.9% | 5.6% |
| space5 | | | |
| Household Size | 2.21 | 2.30 | 2.60 |
| Households | 4,361 | 25,000 | 124,010,992 |
| Family Households | 2,818 | 14,475 | 80,755,759 |
| Married couple, w/children | 23.4% | 29.5% | 30.5% |
| Married couple, no children | 51.1% | 44.8% | 42.9% |
| Non Family Households | 1,543 | 10,525 | 43,255,233 |
| Single householder, w/children | 21.7% | 20.5% | 15.8% |
| Single householder, no children | 3.8% | 5.3% | 10.8% |