Kauaʻi County is a county in the U.S. state of Hawaiʻi. It consists of the islands of Kauaʻi, Niʻihau, Lehua, and Kaʻula. As of the 2010 Census the population was 67,091. The county seat is Līhuʻe.
According to the U.S. Census Bureau, the county has a total area of 1,266 square miles (3,280 km), of which 620 square miles (1,600 km) is land and 646 square miles (1,670 km) (51.0%) is water. The Pacific Ocean surrounds the county.
As of the census of 2000, there were 58,463 people, 20,183 households, and 14,572 families residing in the county. The population density was 94 people per square mile (36/km²). There were 25,331 housing units at an average density of 41 per square mile (16/km²). The racial makeup of the county was 29.5% White, 0.3% Black or African American, 0.4% Native American, 36.0% Asian, 9.1% Pacific Islander, 0.9% from other races, and 23.8% from two or more races. 8.2% of the population were Hispanic or Latino of any race.
There were 20,183 households out of which 34.0% had children under the age of 18 living with them, 53.9% were married couples living together, 12.8% had a female householder with no husband present, and 27.8% were non-families. 21.4% of all households were made up of individuals and 7.7% had someone living alone who was 65 years of age or older. The average household size was 2.87 and the average family size was 3.34.
In the county, the population was spread out with 26.4% under the age of 18, 7.1% from 18 to 24, 27.2% from 25 to 44, 25.5% from 45 to 64, and 13.8% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 100.10 males. For every 100 females age 18 and over, there were 97.50 males.