Selah is a city in Yakima County, Washington, United States. It is north of Yakima and part of its metropolitan area. The city's population was 8,…Selah is a city in Yakima County, Washington, United States. It is north of Yakima and part of its metropolitan area. The city's population was 8,153 at the 2020 census. The name Selah originates from an indigenous word meaning "still water" or "smooth water".