By the early 1870s the Penrhyn Quarry Railway was no longer able to keep up with the output of the Penrhyn quarry. By 1874 the decision had been made to replace the railroad with a steam locomotive worked railway without rope-hauled inclines. Steam locomotives had already been introduced with great success on the quarry's internal railway system and at the nearby Dinorwic Quarry. The Ffestiniog Railway's example had shown that running a 2 ft gauge line for several miles from quarry to sea was perfectly feasible, and that company's Charles Easton Spooner was retained to survey and map possible routes to the port. The Penrhyn directors saw every reason not to follow the Padarn Railway's example and build a main line built to a gauge of 4 ft, joining lines in its quarries to lines in its dock both at a much narrower gauge. All Penrhyn tracks were of the same narrow gauge, so no costly and inefficient internal trans-shipments were needed. At the end of 1875 the first "mainline" locomotive was delivered to Port Penrhyn and moved to the quarry workshops at Coed y Parc. The railroad was converted into the new railway in five stages from 1877 to 1878.