Leeds is a city in West Yorkshire, England. It is the largest settlement in Yorkshire and the administrative centre of the City of Leeds Metropolitan Borough, which is the second most populous district in the United Kingdom. It is built around the River Aire and is in the eastern foothills of the Pennines. The city was a small manorial borough in the 13th century and a market town in the 16th century. It expanded by becoming a major production centre, including of carbonated water where it was invented in the 1760s, and trading centre (mainly with wool) for the 17th and 18th centuries.