Stage 1: Hyesan–Manp'o

In 1959, the Korean State Railway opened the Unbong Line, a 45.6 km (28.3 mi) line from Manp'o to Unbong, to assist with the construction of the Unbong Dam on the Yalu River which had begun in October of that year. The first stage of the northern trunk line, from Manp'o to Hyesan, made use of the entirety of the Unbong Line. A new passenger-friendly station was built at Unbong, called Sinunbong Station (="New Unbong Station")^[3] (the previous Unbong Station, which had been the terminus of the Unbong Line and, after the construction of the new line, became the terminus of the truncated Unbong Line, was later renamed Kuunbong Station - that is, "Old Unbong Station", and Sinunbong Station became simply Unbong Station). Work on the first stage was started at both ends in 1981;^[2] construction went slowly, with the 17.9 km (11.1 mi) from Sinunbong to Chasŏng and the 83.2 km (51.7 mi) from Hyesan to Huju being completed only on 27 November 1987.^[3] Kim Jong Il ordered the formation of youth work brigades who, moving over 10,000,000 m³ (350,000,000 cu ft) of earth and blasting millions of cubic metres of rock,^[4] completed construction of the final 102.5 km (63.7 mi) section between Chasŏng and Huju in 1988.^[5]

Stage 2: Hyesan–Musan

A second stage, a 74 km (46 mi) long line from Hyesan to Musan on the Musan Line via Poch'ŏn, Samjiyŏn, Taehongdan and Musan counties was planned and construction was started,^[3] but was subsequently suspended. The line was to have shared the track of the Paektusan Ch'ŏngnyŏn Line from Hyesan to Wiyŏn; from there, the Wiyŏn–Karim section of the narrow-gauge Samjiyŏn Line and the Karim–Poch'ŏn section of the Poch'ŏn Line were to have been converted to standard gauge; from Poch'ŏn a new line would have been built to Rimyŏngsu, and from there, the Rimyŏngsu–Samjiyŏn–Motka section of narrow-gauge line was to have been regauged. From Samjiyŏn there was to be a new line built via Taehongdan town, Nongsa-rodongjagu, and Samjang-rodongjagu to Hŭngam on the Paengmu Line, from where the existing narrow-gauge line to Musan was to have been regauged.^[3]

Stage 3: Musan–Hoeryŏng

The third stage of the Pukbunaeryuk Line project was to have been the construction of a new 61 km (38 mi) line from Musan to Hoeryŏng on the Hambuk Line. From Musan, the line was to have run through Musan County along the Tumen River via Ch'ilsŏng-ri and Saegŏl-li, continuing from there along a newly built line to Yusŏn, the terminus of the Hoeryŏng Colliery Line; this line would have been absorbed into the Pukpu Line.^[3]

Present

The first stage had been completed at the end of 1988; by then, some works had begun on the second stage, but due to the DPRK's economic crisis of the 1990s, construction was eventually abandoned. Electrification of the existing portion of the line was begun in 1991 with the goal of completing it in time for Kim Il Sung's 80th birthday on 15 April 1992;^[2] however, it wasn't until 1993 that the electrification of the entire Manp'o–Hyesan line was completed.^[4]

By the end of the 2000s, the line was in such poor condition that the operation of trains was nearly impossible; citing this, in April 2011 Kim Jong Il once again mobilised work brigades of the Kim Il-sung Socialist Youth League to undertake the reconstruction of the line; the refurbishment work was completed in November 2013.^[4]