The original demarcation line between North Korea and South Korea roughly follows which northern latitude?

The 38th parallel north is a circle of latitude that is 38 degrees north of the Earth's equatorial plane. It crosses Europe, the Mediterranean Sea, Asia, the Pacific Ocean, North America, and the Atlantic Ocean. The 38th parallel north formed the border between North Korea and South Korea prior to the Korean War.

In 1948, this parallel became the boundary between the two countries, both of which claim to be the government of the whole of Korea. On 25 June 1950, after a series of cross-border raids and gunfire from both the Northern and the Southern sides, the North Korean Army crossed the parallel and invaded South Korea. This sparked a United Nations resolution against the aggression and the Korean War, with United Nations troops helping to defend South Korea.

A 1953 armistice established a Military Demarcation Line which crosses the 38th parallel north, from the southwest to the northeast. The Demarcation Line acts as the boundary now and is often confused with being the 38th parallel north, but the two are not the same.