According to the U.S. Census Bureau, the county has a total area of 2,280 km² (880 mi²). 2,191 km² (846 mi²) of it is land and 89 km² (34 mi²) of it is water. The total area is 3.89% water.
As of the census2 of 2000, there are 153,406 people, 58,212 households, and 43,484 families residing in the county. The population density is 70/km² (181/mi²). There are 64,281 housing units at an average density of 29/km² (76/mi²). The racial makeup of the county is 90.87% White, 0.41% Black or African American, 1.65% Native American, 1.09% Asian, 0.08% Pacific Islander, 4.08% from other races, and 1.82% from two or more races. 8.78% of the population are Hispanic or Latino of any race.
There are 58,212 households out of which 34.40% have children under the age of 18 living with them, 63.00% are married couples living together, 8.20% have a female householder with no husband present, and 25.30% are non-families. 21.10% of all households are made up of individuals and 8.50% have someone living alone who is 65 years of age or older. The average household size is 2.60 and the average family size is 3.01.
In the county the population is spread out with 26.60% under the age of 18, 8.60% from 18 to 24, 29.40% from 25 to 44, 21.10% from 45 to 64, and 14.30% who are 65 years of age or older. The median age is 35 years. For every 100 females there are 97.40 males. For every 100 females age 18 and over, there are 94.90 males.
The median income for a household in the county is $40,281, and the median income for a family is $45,235. Males have a median income of $30,327 versus $22,469 for females. The per capita income for the county is $19,377. 10.10% of the population and 7.30% of families are below the poverty line. Out of the total people living in poverty, 13.80% are under the age of 18 and 7.30% are 65 or older.