Although a 20th-century creation, the borough has Neolithic, Bronze Age and Roman heritage. It encompasses several former mill towns, which expanded and coalesced during the late 19th century as a result of population growth and advances in textile manufacture during the Industrial Revolution. Although some parts contiguous with the city of Manchester are highly industrialised and densely populated, about two-thirds of the borough is composed of rural open space; the eastern half stretches across the South Pennines.