When it was built between 1951 and 1954, the QNS&L connected the port of Sept-Îles on the north shore of the St. Lawrence River with the northern terminus at IOC's mining community of Schefferville, Quebec, a distance of 359 miles (578 km).

In the 1980s, the Schefferville mining operations were closed in favour of iron ore deposits located further to the south near Wabush, and most residents relocated to Labrador City.

QNS&L still provides freight services, transporting employee automobiles, various bulk mine materials, large equipment, and everyday supplies for Labrador City and the various maintenance of way camps.

[1] Since August 20, 2013 the QNS&L has been the only remaining freight railway in Canada to use Single Person Train Operation (SPTO).

[nb 1] On Thursday, November 6, 2014, a freight train consisting of three locomotives and 240 railcars derailed 20 km north of Sept-Îles, because of a landslide over the rail tracks.

The construction of the QNSX forms the backdrop for English author Hammond Innes' 1958 adventure novel about Labrador, The Land God Gave to Cain.