Sheffield is a city and metropolitan borough in South Yorkshire, England. Historically part of the West Riding of Yorkshire, its name derives from the River Sheaf, which runs through the city. With some of its southern suburbs annexed from Derbyshire, the city has grown from its largely industrial roots to encompass a wider economic base. The population of the City of Sheffield is 577,800 and it is one of the eight largest regional English cities that make up the Core Cities Group. Sheffield is the third-largest English district by population. The metropolitan population of Sheffield is 1,569,000.
The city is in the eastern foothills of the Pennines, and the valleys of the River Don and its four tributaries, the Loxley, the Porter Brook, the Rivelin and the Sheaf. 61% of Sheffield's entire area is green space, and a third of the city lies within the Peak District national park. There are more than 250 parks, woodlands and gardens in the city, which is estimated to contain around 4.5 million trees.
In the 19th century, Sheffield gained an international reputation for steel production.