Chehalis is a city in Lewis County, Washington, United States. The population was 7,259 at the 2010 census. It is the county seat of Lewis County. Chehalis began as a settlement around a warehouse beside a railroad track in 1873, when the Northern Pacific Railroad built northward from Kalama to Tacoma, and ignored Claquato, then the county seat three miles to the west. After the Northern Pacific bypassed Claquato, the county seat was moved to Chehalis, leaving Claquato little more than a historical landmark. By 1874, a store was added to the warehouse, and several houses were constructed. The new town was first named Saundersville, for S.S. Saunders, on whose donation land claim it was founded. In 1879, the name was changed to Chehalis, named after the Chehalis people. Chehalis was incorporated on November 23, 1883.