Rainier is a city in Columbia County, Oregon, United States. The city's population was 1,895 at the 2010 census. Rainier is on the south bank of the Columbia River across from Kelso and Longview, Washington.
Rainier was founded in 1851 on the south bank of the Columbia River by Charles E. Fox, the town's first postman. First called Eminence, its name was later changed to Fox's Landing and finally to Rainier. The name Rainier was taken from Mount Rainier in Washington, which can be seen from hills above the city. Rainier was incorporated in 1881.
For much of the last quarter of the twentieth century, Rainier was known to the rest of Oregon as home to Trojan Nuclear Power Plant, the only commercial nuclear reactor in the state, which supplied electricity to Portland and its suburbs starting in March 1976. This reactor was closed periodically due to structural problems, and in January 1993, it was decommissioned after cracks developed in the steam tubes. On May 21, 2006, the cooling tower was demolished.
The closing of the Trojan plant set off a decline in the number of businesses in the city.