The peak is situated 80 miles north of the Arctic Circle, five miles east of Dalton Highway, 11.3 mi (18 km) south of Sukakpak Mountain, and 190 mi (306 km) north-northwest of Fairbanks.

The peak was named about 1930 by wilderness activist Robert Marshall after "Poss" Postlethwaite, an early and old gold prospector in this area around Wiseman.

[3] Robert Marshall described the then 78-year-old Postlethwaite as "the oldest man in the Koyukuk," having spent 32 winters in the area.

Precipitation runoff from the mountain drains into tributaries of the Middle and South Forks of Koyukuk River.

The months June through August offer the most favorable weather for viewing and climbing.