St. Helens is the county seat of Columbia County, Oregon. It was founded by Captain Henry Montgomery 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, roughly 39 miles away in Washington. The city is about 28 miles northwest of Portland. Its population was 12,883 at the 2010 census.