Arch Rock was a natural arch formation located just south of Topanga Canyon [1] along the coast of Santa Monica Bay, Los Angeles County, California in the United States.
Arch Rock was located at what is now 18412 Pacific Coast Highway. [2] It was a popular destination for day trips from the young town of Santa Monica. [3] The arch collapsed or was surreptitiously demolished the evening of March 24, 1906, possibly because it was an inconvenient obstacle to creating a coast route for the new-fangled automobiles. [4] Another account says a railroad crew dynamited the formation under cover of darkness. [2] A coach route had previously traveled right under the arch but was only accessible at low tide. [5]
Nearby Castle Rock was demolished as part of a road expansion project in 1945. [2]