Arch Cape is an unincorporated community in Clatsop County, Oregon, United States. Named for the natural arch in the coastal rocks and the headland that extends into the Pacific Ocean, it is located along the Pacific coast, approximately four miles south of Cannon Beach, between Hug Point State Recreation Site to the north and Oswald West State Park to the south.Castle Rock, a large castle-shaped monolith formed by lava flows millions of years ago, sits just off the coast of Arch Cape.According to "The Oregon Companion" by Richard H. Engeman, Arch Cape was a "remote hamlet...at the end of a wagon road from Seaside, Oregon." The 2000 US Census showed that Arch Cape had a population of 205.Prior to 1938, U.S. Route 101 in Oregon, which was completed in 1936, ended at Arch Cape, just south of Arch Cape Creek. In February 1936, the Oregon State Highway Commission began work on a 1,228-foot tunnel through Neahkahnie Mountain.