The land of Musan is high and more than 90% is mountainous and uninhabited; much of it lies on the Paekmu Plateau, while the northwest makes up part of the Musan Plateau. The Hamgyong Mountains pass along the county's northwest flank. Musan is the coldest region in North Hamgyong.
The Musan area has long been known for iron ore mines, lumber, and potatoes. The Musan Mine, a major excavator of iron ore, is located here.