Built to transport coal from various mines to the ports of Sydney and Louisbourg, the S&L operated in the eastern part of Cape Breton County, Nova Scotia.

Upon taking control of Ile Royale, Britain renamed it to Cape Breton Island and merged the territory into the Colony of Nova Scotia.

In 1788, King George III authorized his son, Prince Frederick, the Duke of York, to be granted the mineral rights to Nova Scotia (then only the peninsular portion), however events such as the Napoleonic Wars put the application on hold until the end of conflict in 1815.

At that time, the Duke was in financial difficulty and had an agent apply for the mineral rights which the King had authorized, however the paperwork was misplaced.

In 1825 the unfinished application was discovered and approved (for all of Nova Scotia, including Cape Breton Island), whereby the Duke signed over the rights to the General Mining Association, a wholly owned subsidiary of one of the Duke's creditors: the London jewelry firm of Rundell, Bridge and Rundell.

Between 1858-1870, the GMA opened 19 underground mines in the Sydney Coal Field, with most production destined for export to the northeastern United States.

In addition to the GMA, many independently owned collieries opened in the Sydney Coal Field after 1858, including several US-financed operations at New Victoria, Bridgeport, and Reserve Mines.

Although Sydney had a much more suitable harbour than Louisbourg, the former was frequently choked by heavy sea ice during the important coal-shipment season throughout the winter months.

Mining employment reached a peak on Cape Breton Island immediately prior to World War I and the dawn of increased mechanization of the underground collieries.

[1] Coal production peaked during World War II in the early 1940s and began to drop dramatically with the advent of internal combustion engines and other sources of heat.

In response to a vast public outcry in industrial Cape Breton County, the Minority government of Prime Minister Lester Pearson announced J.R. Donald would head a Royal Commission of Inquiry into the Cape Breton coal industry, with hearings held in 1965 and 1966.

Haslam as general manager, the company operated 39 miles (63 km) of route with offices at Sydney; at that date it owned 15 diesel shunters and 1,100 freight cars.

DEVCO continued operation of the railway until 2001, when it closed the Prince colliery, its last underground coal mine.