The Peak District is an upland area in England at the southern end of the Pennines. Mostly in Derbyshire, it extends into Cheshire, Greater Manchester, Staffordshire, West Yorkshire and South Yorkshire. It includes the Dark Peak, where moorland is found and the geology is dominated by gritstone, and the White Peak, a limestone area with valleys and gorges. The Dark Peak forms an arc on the north, east and west sides; the White Peak covers central and southern tracts. The historic Peak District extends beyond the National Park, which excludes major towns, quarries and industrial areas. It became the first of the national parks of England and Wales in 1951. Nearby Manchester, Stoke-on-Trent, Derby and Sheffield send millions of visitors – some 20 million live within an hour's ride. Inhabited from the Mesolithic era, it shows evidence of the Neolithic, Bronze and Iron Ages. Settled by the Romans and Anglo-Saxons, it remained largely agricultural; mining arose in the Middle Ages. Richard Arkwright built cotton mills in the Industrial Revolution. As mining declined, quarrying grew. Tourism came with the railways, spurred by the landscape, spa towns and Castleton's show caves.