At the time, the Lewis and Clark Expedition recorded a different river draining the plains which entered the Pacific near the current day Camp Rilea Armed Forces Training Center.

Joseph H. Frost established a Methodist mission there in 1841 and built homes for their families on Clatsop Plains.

The Pioneer cemetery established in 1846, making it the oldest in the county, is the burial place for many early settlers.

A community called "Clatsop Plains" was established and incorporated in 1870, primarily for the purpose of restricting cattle grazing along the sea ridge.

[5] The coastal grassy areas of Clatsop Plains was home to the endangered Oregon silverspot butterfly.