Some of the world's great cities are linked in the popular mind with their river and, for reasons both ancient and modern, Liverpool and the Mersey are inseparable. Treacherous and fast flowing, with a huge tidal range, the Mersey nevertheless formed part of the chain that carried the trade of the world, linking large parts of northern and midland England with markets and sources of supply across the globe. For centuries, this traffic passed through Liverpool, the landing point for imports and the port of dispatch for goods sent overseas or around the coast. Liverpool developed to serve a growing national and international trading network and for many decades handled more of the cargoes of Britain's maritime even than London. In Liverpool, the warehouse represents the essential function of the city and nowhere else can the evolution of this important building type be studied in such depth from surviving buildings.