Where was the coast of Washington millions of years ago?

Millions of years ago, the coast of Washington was located much farther inland due to the movement of tectonic plates. During the Late Cretaceous period, for instance, the region was covered by a shallow sea known as the Western Interior Seaway. Over time, geological processes such as tectonic uplift and erosion shifted the coastline to its current position along the Pacific Ocean. The landscape has been shaped significantly by volcanic activity, glaciation, and other geological forces since then.