Sheffield is the fourth largest city in England, and is situated in the South West of the county of South Yorkshire. The name Sheffield derives from the Anglo-Saxon, and means fields around the river Sheaf, and the town is referred to as Escafield in the Domesday Book. The city was the site of a medieval castle founded by the Normans, and later destroyed in the English civil war. Production of knives and cutlery in the town can be traced back as far as the 14th century. Although Sheffield did not become world famous for metalworking until it started producing steel in the 18th century. In the early 20th century, Harry Brearley of Sheffield invented Stainless Steel, and the city still has a large steel industry to this day.