Skamania County is a county located in the U.S. state of Washington. As of the 2010 census, the population was 11,066. The county seat and largest incorporated city is Stevenson, although the Carson River Valley CDP is more populous. The county was founded in 1854 and derives its name from the Cascades Chinook word sk'mániak, meaning "swift waters".Skamania County is included in the Portland-Vancouver-Hillsboro, OR-WA Metropolitan Statistical Area.