'The Golden Valley'. In the 20th century the population declined from 19,000 in the 1911 census to 15,000 in the 1971 census. The 2001 census recorded a population of 16,849 living in the town. Industrial Quarrying Haslingden is notable for its stone quarrying, and Haslingden Flag (a quartz-based sandstone) was distributed throughout the country in the 19th century with the opening up of the rail network. This stone was used in the paving of London, including Trafalgar Square. Flagstone is a type of sedimentary rock, relatively easy to split or quarry in slabs, and hence ideal for paving. Locally it is also used for making fences and roofing. Geologists have found that it has a hardness and silica content not unlike granite, and its presence was the main reason for the growth of quarrying in Rossendale. Haslingden Flag is unique; two other, common types of flagstone ('rough rocks') are found throughout the Pennines, but a third type is found only in the local Haslingden Flags. Textiles Like much of East Lancashire, Haslingden has a long association with the textile industry. From the 16th century, after the old Forest of Rossendale was opened up to settlement, farmers raised sheep on the moorlands and made woollen cloth. Initially this was small-scale and local but towards the end of the 18th century cloth workers came together to work in small groups of houses. At the same time advances in technology meant that the first mills were appearing in the area. Most of these were small, water-powered buildings; and Haslingden, with its elevated situation, was not a natural place for the development of these early mills. Locally they were situated lower down in the river valleys, such as at nearby Helmshore. The long association with wool meant that Haslingden and the other Rossendale towns had expertise with the processes of cloth production, and so were able to switch easily to cotton weaving. Cotton was better suited than wool to industrialised spinning as its fibres were less likely to break than wool. Cotton cloth manufacture quickly became a highly successful industry, and its development was closely associated with its role in the expansion of the slave trade. African slaves being bartered for cotton goods, and cotton being picked by slaves in the Deep South of the U.S. The growth of mills also had an enormous impact on the landscape, and on the lives of its