Dewey Peak is a summit located on the shared border of Mount Rainier National Park and William O. Douglas Wilderness. It is also on the shared border of Pierce County and Yakima County in Washington state. Dewey Peak is situated on the crest of the Cascade Range southeast of Chinook Pass, east of Seymour Peak, and northeast of Shriner Peak. Its nearest higher peak is Chinook Peak, to the north. Dewey Peak is named in association with Dewey Lake which is set below its north aspect. Precipitation runoff from Dewey Peak drains into tributaries of the Cowlitz River and Yakima River.