The Sind-Pishin State Railway was a broad gauge line that ran up to the border with Afghanistan. In 1886 it was amalgamated with other railways to form the North-Western State Railway. In 1885, the Sindh, Punjab and Delhi Railways were purchased by the Secretary of State for India. On 1st January, 1886 this line and other State Railways (the Indus Valley, the Punjab Northern, inclusive of Sindh Sagar Eastern section, and the Kandahar or Sindh-Pishin Southern section) were integrated and North Western State Railway was formed; which was later on renamed as North Western Railways (NWR).
With Ruling Gradient of 1 in 40 and 45, the Sind-Pishin State Railway is one of the Hill Railway line during British era. The first line to be constructed to Quetta was on the Sind-Pishin State Railway, but of a comparatively light standard. The heaviest engines allowed over it are the new Indian standard light 4-6-2 XA’s, which have only 13-ton axle loads. Single throughout, this line is about 120 miles in length. In that distance it mounts over 6,000 vertical feet, with a ruling gradient of 1 in 40-45. Two outstanding engineering features on this route are the Chappar Rift and the Mud Gorge. The former is a deep cleft in the country about three miles long, with vertical cliffs 200 ft. to 300 ft. in height, which cuts across the ridge separating two valleys. The line uses it to pass from one of the valleys to the other, but this bold policy involves nine tunnels 6,400 ft. in aggregate length, a seven-span viaduct and the famous Margaret Louise bridge, which is 250 ft. high and consists of one 150 ft. and eight 40 ft. spans. The Mud Gorge is a very steep narrow valley, five miles long, with most treacherous soil, mostly gypsum, that becomes a sludge and slips down the valley when there is any rain. The only practicable way to control the landslides was to line the gorge with masonry, after some considerable difficulty and at great cost.