Wasatch County is part of the Heber Micropolitan Statistical Area as well as the Salt Lake City–Ogden–Clearfield Combined Statistical Area.
As of the census of 2000, there were 15,215 people, 4,743 households, and 3,870 families residing in the county. The population density was 13 people per square mile (5/km²). There were 6,564 housing units at an average density of 6 per square mile (2/km²). The racial makeup of the county was 95.62% White, 0.22% Black or African American, 0.43% Native American, 0.30% Asian, 0.10% Pacific Islander, 1.96% from other races, and 1.38% from two or more races. 5.09% of the population were Hispanic or Latino of any race.
By 2005 90.0% of the county population was non-Hispanic whites. African-Americans were 0.5% of the population, a higher percentage than in neighboring Utah County. This also represented a more than 100% growth in the African American population of the county. Native Americans were now 0.8% of the population, also approaching a percentage growth of nearly 100%. Asians made up 0.6% of the population, also a large percentage growth. Latinos were 7.7% of the population, not as large a percentage growth but still a growth of over 200 people, large by Wasatch county standards.
There were 4,743 households out of which 46.20% had children under the age of 18 living with them, 71.00% were married couples living together, 7.50% had a female householder with no husband present, and 18.40% were non-families. 14.30% of all households were made up of individuals and 5.00% had someone living alone who was 65 years of age or older. The average household size was 3.18 and the average family size was 3.55.
In the county, the population was spread out with 34.20% under the age of 18, 9.90% from 18 to 24, 29.00% from 25 to 44, 18.50% from 45 to 64, and 8.40% who were 65 years of age or older. The median age was 30 years. For every 100 females there were 103.30 males. For every 100 females age 18 and over, there were 99.50 males.
The median income for a household in the county was $49,612, and the median income for a family was $52,102. Males had a median income of $37,399 versus $23,571 for females. The per capita income for the county was $19,869. About 4.20% of families and 5.20% of the population were below the poverty line, including 5.60% of those under age 18 and 4.00% of those age 65 or over.