St. Helens is the county seat of Columbia County, Oregon. It was founded by Captain H. M. Knighton, a native of New England, in 1845 as "Plymouth". The population was 12,883 at the 2010 census.
St. Helens was established as a river port on the Columbia River in the 1840s. In 1853, the Pacific Mail Steamship Company tried to make the city their only stop on the Columbia River.Portland's merchants boycotted this effort, and the San Francisco steamship Peytona helped break the impasse.St. Helens was incorporated as a city in 1889.The Lewis and Clark Expedition passed through and camped in the area that is now St. Helens on the night of November 5, 1805 while on their way to the Pacific Ocean. While here the party encountered Native Americans and Clark observed "low rockey clifts".