Marrowstone is a census-designated place on Marrowstone Island in Jefferson County, Washington, United States. The population was 995 at the 2020 census. All Marrowstone addresses are in Nordland, Washington, and the ZIP code is 98358. Marrowstone takes its name from Marrowstone Point, the northernmost point on Marrowstone Island. It was given the name "Marrow-Stone Point" in 1792 by the British explorer, George Vancouver, in describing the area's hard, clay-like soil.