This 327 foot monolith is known by two names, Haystack Rock and Chief Kiawanda Rock, but its similarity to another Haystack Rock up the coast at Cannon Beach makes it a neat place to stop and see. It actually mirrors its smaller 237 foot namesake 60 miles away, but they appear the same size due to its location farther out in the ocean. Cape Kiwanda Natural Area is a good place from which to view it.
If you go:
If you want to get up closer, you must exit Route 101 and go to either the cape or to Pacific City, both worth the small detour.
Links:

33180 Cape Kiwanda Drive
Pacific City, Oregon 97115 USA
Phone Numbers:
Cape Kiwanda
+1 (503) 842-3182
+1 (503) 842-3182