Within North Korea, it borders Ch'angsŏng to the east, Ch'ŏnma and Taegwan to the south, and Ŭiju to the west.

The Kangnam Mountains rise in the southeast of Sakju with its highest peak Munsan at 1046 m. The overall terrain is rugged, with only 13% of the county's area under cultivation, as compared to 80% which is forested.

Livestock farming is important to the local economy; Sakju leads the province in the number of hogs raised.

The P'yŏngbuk Line of the Korean State Railway passes through the county, on its way to Chŏngju from Ch'ŏngsu (청수).

Some of North Korea's chemical weapons factories are located in the city under the control of the Thirty-second Division.