Hwanghae Province was reorganized into Kōkai-dō, with Kaishū (Haeju) serving as its capital.

[3] In 1945, Korea was divided into Soviet and American zones of occupation, north and south respectively of the 38th parallel.

In 1953, at the end of the Korean War, the Northern Limit Line was established, which marked the maritime boundary between North and South Korea.

The line runs between the mainland portion of Gyeonggi Province that had been part of Hwanghae before 1945, and the adjacent offshore islands (the largest of which is Baengnyeongdo).

As a result, the mainland portion reverted to North Korean control, while the islands remained a part of South Korea.