They are sites for salt production in the area of Wonup workers' district in Onchon County of Nampho City, and Wondong Dolmen in Township of Yonsan County and Taechon Dolmen in Rinsan County of North Hwanghae Province and four other dolmens.

It was confirmed that sites for salt production were used by people of Josonhuguk (first century-second century).

The dolmens are typical remains representing the times of Tangun Korea.