The Llanelly and Mynydd Mawr line opened in 1881, worked by the contractor, John Waddell, who had built the line and taken a majority of the shares. The fortunes of the company were closely bound with those of the mineral industries, which fluctuated considerably. The Company considered operating a public passenger service but never did so, although workmen's trains were operated for some years. The decline of coal mining in the area seemed to be reversed when the huge new Cynheidre Pit was established in the 1960s, but the railway capacity enhancements to deal with the expected upsurge in traffic proved to be unnecessary. The line closed completely in 1989.