Carreg y Llam quarry was established in the valley in the 19th century and granite was then in great demand for road building. The three Nant quarries became part of the Welsh Granite Company in 1911. But tarmac became the preferred road surface from the early 20th century and the demand for granite declined. The Welsh Granite Co. closed the quarries in the 1940s. Some quarrying continued in the 1950s. These trucks are from the British Quarrying Company c1950.