The lake covers 19 acres, with a mean depth of 16 feet and a maximum depth of 31 feet. Until 1913, a sawmill was located at its southwest corner. Tannic acid from logs dumped into the lake gave its water a bitter taste and the lake itself a name. The Duwamish called the lake "Blackcaps on the Sides" (Lushootseed: cHálqWadee), denoting the blackcap (Rubus leucodermis) plants that grew along the shores. It is a glacial lake, its basin having been dug by the Puget Lobe of the Cordilleran Ice Sheet, which also created Lake Washington, Union, Green and Haller Lakes.