Jefferson County, Washington, United States. The population was 10,148 at the 2020 United States Census. It is the county seat and only incorporated city of Jefferson County.retrieved2024-01-01tagsPort Townsend, WashingtonJefferson County, Washington (Wikipedia)Washington (state) (Wikipedia)United States (Wikipedia)Wikipediawebsitehttps://en.wikipedia.org/wiki/Port_Townsend,_Washington