Clatsop Spit is a giant sand spit on the Pacific coast along U.S. Route 101 between Astoria and the north end of Tillamook Head in Clatsop County, northwest Oregon at the mouth of the Columbia River. The Clatsop Spit was formed by Columbia River sediment brought to the coast by the river flow after the last ice age ended approximately 8500 years ago and the ocean level rose. Here it was worked over and shaped by the wind and the waves until a vast and sandy plain was formed.In regular conversation, referring to Clatsop Spit usually refers to the northern end of the spit: the area that is bound by the Pacific to the west and the Columbia River to the northeast. In the past, the spit was known as Clatsop Sands.