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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 name was changed to St. Helens in the latter part of 1850 for its view of Mount St. Helens some away in Washington. The population was 10,019 at the 2000 census.
St. Helens was established as a river port on the Columbia River in the 1840s, and was the primary deep-water port, surpassing Portland until the destruction of the mail docks by fire. The docks burned down twice under mysterious circumstances, after which Portland became the primary port. St. Helens was incorporated as a city in 1889.