Between South and Middle Forks of Koyukuk River, 33 mi. W of Chandalar; Brooks Range
Named about 1930 by Robert Marshall for Poss Postlethwaite, one of the oldest prospectors in the region.
Glacier Lake, Linda Creek Lake, Minnie Creek Lake, Winers Lake,
Mountains:Dillon Mountain, Poss Mountain, Sukakpak Mountain, Wiehl Mountain,
Mountain Passes:Rivers:Bettles River, Dietrich River, Mathews River,
Streams:Bore Creek, Boulder Creek, California Creek, Canyon Creek, Eider Creek, Emery Creek, Gold Creek, Linda Creek, Magnet Creek, Nugget Creek, Over Creek, Ready Bullion Creek, Sheep Creek, Vi Creek, Wolf Pup,
Valleys: