Goldendale, Washington. Goldendale is a rural agricultural city and county seat of Klickitat County, Washington, United States,[6] near the Columbia River Gorge. The population within city limits was 3,760 at the 2000 census and 3,407, a 9.4% decrease at the 2010 census. A nationally known point of interest is north of town, Goldendale Observatory State Park. The valley area in which Goldendale is located offers a sweeping and dramatic views of the Cascade Range Mountains 40 mile to the west and the Simcoe Hills to the north.