Grays Harbor County was formed out of Thurston County on April 14, 1854. Originally named Chehalis County, it took its present name in 1915.
As of the census of 2000, there were 67,194 people, 26,808 households, and 17,907 families residing in the county. The population density was 35 people per square mile (14/km²). There were 32,489 housing units at an average density of 17 per square mile (7/km²). The racial makeup of the county was 88.30% White, 0.34% Black or African American, 4.66% Native American, 1.22% Asian, 0.11% Pacific Islander, 2.27% from other races, and 3.10% from two or more races. 4.85% of the population were Hispanic or Latino of any race. 16.3% were of German, 11.9% United States or American, 9.9% English, 9.2% Irish and 6.1% Norwegian ancestry according to Census 2000. 94.1% spoke English and 3.9% Spanish as their first language.
There were 26,808 households out of which 30.50% had children under the age of 18 living with them, 50.70% were married couples living together, 11.10% had a female householder with no husband present, and 33.20% were non-families. 26.70% of all households were made up of individuals and 11.60% had someone living alone who was 65 years of age or older. The average household size was 2.48 and the average family size was 2.98.
In the county, the population was spread out with 25.70% under the age of 18, 7.90% from 18 to 24, 26.00% from 25 to 44, 25.00% from 45 to 64, and 15.40% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 98.80 males. For every 100 females age 18 and over, there were 96.20 males.
The median income for a household in the county was $34,160, and the median income for a family was $39,709. Males had a median income of $35,947 versus $24,262 for females. The per capita income for the county was $16,799. 16.10% of the population and 11.90% of families were below the poverty line. 21.60% of those under the age of 18 and 9. 40% of those 65 and older were living below the poverty line.