Haystack Rock is one of the most iconic landmarks in Oregon, if not all of the United States. This giant monolith located off the shore of Cannon Beach is the largest intertidal sea stack in all of the United States. This impressive feature formed as the result of large volcanic eruptions that occurred in eastern Oregon roughly 15 million years ago and subsequent wave erosion. Have you been to Haystack Rock? #geography #geology #oregon #pnw #stem | Mountain Facts