The lake covers 19 acres (77,000 m²), with a mean depth of 16 feet (5 m) and a maximum depth of 31 feet (9 m). 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.
The lake is situated between Greenwood Avenue North to the west, Linden Avenue North to the east, North 137th Street to the north, and North 130th Street to the south.