town in the unitary authority of Halton, historic county of Lancashire, England. It is situated on the north bank of the River Mersey at its lowest bridging point and on the southern periphery of the Liverpool metropolitan region. The modern town is a result of 19th-century industrial expansion and is a principal centre of the British chemical industry, largely because of the proximity of the Cheshire salt fields and the Lancashire coalfield. Pop. (2001) 55,686.