Native Americans called the lake Smokiam, which means "healing waters". Settlers later changed the name to Soap Lake in an effort to characterize the soapy texture of the water.
Soap Lake has mineral content thought to be of therapeutic value. The water is made up of seventeen minerals. By bathing in the water, these mineral salts affect the body in such a way as to relieve many rheumatic and skin conditions such as psoriasis, arthritis, muscular pains and nervousness.
The lake water is piped into many of the town's hotels and motels. Public beaches and swimming in Soap Lake is convenient to the public.
Soap Lake is in Grant County, northeast of Ephrata. Highway 17 goes south to Moses Lake and north along the Lower Grand Coulee to Highway 2, Coulee City and Banks Lake.