Soap Lake is a city in Grant County, Washington, on the shores of Soap Lake. The population was 1,514 at the 2010 census.
Soap Lake was officially incorporated on June 9, 1919.
The choosing of the town's name ended the battle between two rival factions. One group had platted a town site and called it Siloam in 1905; while another faction named their town-to-be Cottage City on 1908. The name Soap Lake came from the word Smokiam, an Indian term which translates to "Healing Waters". The tribes used the lake for healing purposes for themselves and their animals for many years before the area was settled by pioneers.
At that time, Soap Lake was already a busy resort and health spa. It contained four hotels and many rooming houses and businesses catering to sojourners seeking a cure. The residents were very proud of the two-room schoolhouse built in 1907. Even though Soap Lake's main industry was derived from the medicinal lake, it became a social center.