Seaside is a city in Clatsop County, Oregon, United States, on the coast of the Pacific Ocean. The name Seaside is derived from Seaside House, a historic summer resort built in the 1870s by railroad magnate Ben Holladay. The city's population was 6,457 at the 2010 census.
The Clatsop were a historic Native American tribe that had a village named Ne-co-tat (in their Chinook language) in this area. Indigenous peoples had long inhabited the coastal area.
About January 1, 1806, a group of men from the Lewis and Clark Expedition built a salt-making cairn at the site later developed as Seaside. The city was not incorporated until February 17, 1899, when coastal resort areas were being settled. It is about 79 miles (127 km) by car northwest of Portland, Oregon, a major population center.
In 1912, Alexandre Gilbert (1843–1932) was elected Mayor of Seaside. Gilbert was a French immigrant, a veteran of the Franco Prussian War (1870-1871). After living in San Francisco, California and Astoria, Oregon, Gilbert moved to Seaside where he had a beach cottage (built in 1885). Gilbert was a real estate developer who donated land to the City of Seaside for its one-and-a-half-mile-long Promenade, or "Prom," along the Pacific beach.