Lake Puyallup was a glacial lake that formed as the Puget Sound Glacier retreated northward, trapping meltwater and runoff from Mount Rainier in the Puyallup River valley. At its largest, it was impounded by the ice front across the valley near Tacoma and Auburn. Its earliest outlet ran south through the Ohop channel, past Lake Kapowsin and through Ohop Creek and Ohop Lake toward the Nisqually. Surrounding landforms controlled this drainage and blocked other routes. When the glacier withdrew farther north and opened a lower outlet at Clover Creek, the lake shrank and became known as Lake Tacoma. This lake was part of the evolving ice-margin lakes that shaped southern Puget Sound valleys and drainage.