Kitsap County was formed out of King County, Washington and Jefferson County, Washington on January 16, 1857. Originally named Slaughter County, it was soon renamed.
The United States Navy is of great importance to the county because it is the largest employer in the county, with installations at Puget Sound Naval Shipyard, Naval Undersea Warfare Center Keyport, and Naval Base Kitsap (which comprises former NSB Bangor, and NS Bremerton).
Kitsap County is connected to the eastern shore of Puget Sound by Washington State Ferries runs from Bremerton to Downtown Seattle , Southworth to West Seattle via Vashon Island, Bainbridge Island to Downtown Seattle, and from Kingston to Edmonds
As of the census of 2000, there were 231,969 people, 86,416 households, and 61,355 families residing in the county. The population density was 586 people per square mile (226/km²). There were 92,644 housing units at an average density of 234 per square mile (90/km²). The racial makeup of the county was 84.27% White, 2.87% Black or African American, 1.62% Native American, 4.39% Asian, 0.78% Pacific Islander, 1.43% from other races, and 4.64% from two or more races. 4.14% of the population were Hispanic or Latino of any race. 15.6% were of German, 10.4% English, 9.8% Irish, 7.2% United States or American and 7.0% Norwegian ancestry according to Census 2000. 92.2% spoke English, 2.5% Spanish and 2.2% Tagalog as their first language.
There were 86,416 households out of which 36.00% had children under the age of 18 living with them, 57.70% were married couples living together, 9.50% had a female householder with no husband present, and 29.00% were non-families. 22.60% of all households were made up of individuals and 7.60% had someone living alone who was 65 years of age or older. The average household size was 2.60 and the average family size was 3.05.
In the county, the population was spread out with 26.80% under the age of 18, 9.20% from 18 to 24, 29.60% from 25 to 44, 23.80% from 45 to 64, and 10.60% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 102.70 males. For every 100 females age 18 and over, there were 101.20 males.
The median income for a household in the county was $46,840, and the median income for a family was $53,878. Males had a median income of $39,889 versus $28,586 for females. The per capita income for the county was $22,317. About 6.30% of families and 8.80% of the population were below the poverty line, including 10.90% of those under age 18 and 6.00% of those age 65 or over.