| | Spirit Lake, IA | Newton, IA | United States |
| Population | 5,301 | 15,688 | 329,725,481 |
| Female Population | 52.0% | 49.6% | 50.5% |
| Male Population | 48.0% | 50.5% | 49.5% |
| Median Age | 41.1 | 40.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 4,860 | 15,240 | 309,327,143 |
| Population - 2000 | 4,261 | 15,579 | 285,036,114 |
| Population - 1990 | 3,871 | 14,789 | 251,960,433 |
| Pop. 2000 to Now | 23.2% | -2.9% | 15.6% |
| Pop. 1990 to Now | 35.7% | 2.3% | 30.8% |
| space4 | | | |
| Population Density | 1,179.6 | 1,393.1 | 93.4 |
| Land Area | 4.5 | 11.3 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Spirit Lake, IA | Newton, IA | United States |
| Age 0 to 4 | 4.8% | 6.2% | 5.9% |
| Age 5 to 9 | 8.4% | 6.2% | 6.1% |
| Age 10 to 14 | 6.5% | 7.1% | 6.6% |
| Age 15 to 17 | 2.1% | 4.4% | 3.9% |
| Age 18 to 20 | 2.2% | 3.5% | 4.0% |
| Age 21 to 24 | 7.7% | 4.6% | 5.2% |
| Age 25 to 34 | 12.6% | 12.0% | 13.8% |
| Age 35 to 44 | 8.6% | 9.3% | 12.9% |
| Age 45 to 54 | 11.3% | 13.7% | 12.6% |
| Age 55 to 59 | 5.8% | 5.7% | 6.7% |
| Age 60 to 64 | 6.0% | 6.7% | 6.3% |
| Age 65 to 74 | 13.7% | 9.6% | 9.6% |
| Age 75 to 84 | 4.4% | 6.9% | 4.5% |
| Age 85 and over | 6.1% | 4.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Spirit Lake, IA | Newton, IA | United States |
| White | 92.1% | 90.4% | 59.4% |
| Black | 0.2% | 2.2% | 12.2% |
| Asian | 0.3% | 0.1% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 5.2% | 3.1% | 3.2% |
| Hispanic | 2.2% | 4.1% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Spirit Lake, IA | Newton, IA | United States |
| Married Population | 48.7% | 54.8% | 49.8% |
| Currently Married | 46.9% | 52.3% | 48.0% |
| Married but Separated | 1.8% | 2.5% | 1.8% |
| Single Population | 51.3% | 45.2% | 50.2% |
| Never Married | 30.0% | 26.3% | 33.8% |
| Divorced | 12.1% | 11.8% | 10.8% |
| Widowed | 9.2% | 7.2% | 5.6% |
| space5 | | | |
| Household Size | 2.05 | 2.42 | 2.60 |
| Households | 2,531 | 6,337 | 124,010,992 |
| Family Households | 1,227 | 4,135 | 80,755,759 |
| Married couple, w/children | 31.3% | 25.6% | 30.5% |
| Married couple, no children | 48.3% | 45.2% | 42.9% |
| Non Family Households | 1,304 | 2,202 | 43,255,233 |
| Single householder, w/children | 12.6% | 22.0% | 15.8% |
| Single householder, no children | 7.8% | 7.2% | 10.8% |