The South Jetty at the mouth of the Columbia River took 27 years to build, beginning in 1886. The 6.5-mile jetty helps to contain and trap the shifting sand deposits at the mouth of the river and thus ensure a relatively stable shipping channel. It has been instrumental in the formation of Clatsop Spit, which was a partially submerged shoal before the construction of the jetty.
The jetty stretches across Jetty Lagoon, also called Trestle Bay, from Point Adams out towards the Columbia Bar, and for part of the way is accompanied by the ruins of a wooden trestle, which carried the trains used in the jetty’s construction. Elk are often seen in the grasslands that verge on the lagoon and take shelter in the spit’s thickets.