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 name of the community was changed to St. Helens in the latter part of 1850, after the view of Mount St. Helens across the Columbia River in Washington. The population was 10,019 at the 2000 census. St. Helens apartments for rent comparison page shows most up to date rent information on St. Helens apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.