The area now occupied by the City of Sheffield is believed to have been inhabited since at least the late Upper Paleolithic, about 12,800 years ago. The earliest evidence of human occupation in the Sheffield area was found at Creswell Crags to the east of the city. In the Iron Age the area became the southernmost territory of the Pennine tribe called the Brigantes. It is this tribe who are thought to have constructed several hill forts in and around Sheffield.
Following the departure of the Romans, the Sheffield area may have been the southern part of the Brittonic kingdom of Elmet, with the rivers Sheaf and Don forming part of the boundary between this kingdom and the kingdom of Mercia. Gradually, Anglian settlers pushed west from the kingdom of Deira. A Britonnic presence within the Sheffield area is evidenced by two settlements called Wales and Waleswood close to Sheffield. The settlements that grew and merged to form Sheffield, however, date from the second half of the first millennium, and are of Anglo-Saxon and Danish origin. In Anglo-Saxon times, the Sheffield area straddled the border between the kingdoms of Mercia and Northumbria. The Anglo-Saxon Chronicle reports that Eanred of Northumbria submitted to Egbert of Wessex at the hamlet of Dore (now a suburb of Sheffield) in 829, a key event in the unification of the kingdom of England under the House of Wessex.
After the Norman conquest of England, Sheffield Castle was built to protect the local settlements, and a small town developed that is the nucleus of the modern city. By 1296, a market had been established at what is now known as Castle Square, and Sheffield subsequently grew into a small market town. In the 14th century, Sheffield was already noted for the production of knives, as mentioned in Geoffrey Chaucer's The Canterbury Tales, and by the early 1600s it had become the main centre of cutlery manufacture in England outside London, overseen by the Company of Cutlers in Hallamshire. From 1570 to 1584, Mary, Queen of Scots, was imprisoned in Sheffield Castle and Sheffield Manor.
During the 1740s, a form of the crucible steel process was discovered that allowed the manufacture of a better quality of steel than had previously been possible. In about the same period, a technique was developed for fusing a thin sheet of silver onto a copper ingot to produce silver plating, which became widely known as Sheffield plate. These innovations spurred Sheffield's growth as an industrial town, but the loss of some important export markets led to a recession in the late 18th and early 19th century. The resulting poor conditions culminated in a cholera epidemic that killed 402 people in 1832. The population of the town grew rapidly throughout the 19th century; increasing from 60,095 in 1801 to 451,195 by 1901. The Sheffield and Rotherham railway was constructed in 1838, connecting the two towns. The town was incorporated as a borough in 1842, and was granted a city charter in 1893. The influx of people also led to demand for better water supplies, and a number of new reservoirs were constructed on the outskirts of the town.
The Women of Steel
statue commemorates the women of Sheffield who worked in the city's steel industry during the First and Second World Wars
The collapse of the dam wall of one of these reservoirs in 1864 resulted in the Great Sheffield Flood, which killed 270 people and devastated large parts of the town. The growing population led to the construction of many back-to-back dwellings that, along with severe pollution from the factories, inspired George Orwell in 1937 to write: "Sheffield, I suppose, could justly claim to be called the ugliest town in the Old World".
The Great Depression hit the city in the 1930s, but as international tensions increased and the Second World War became imminent; Sheffield's steel factories were set to work manufacturing weapons and ammunition for the war effort. As a result, the city became a target for bombing raids, the heaviest of which occurred on the nights of 12 and 15 December 1940, now known as the Sheffield Blitz. The city was protected by barrage balloons managed from RAF Norton  More than 660 lives were lost and many buildings destroyed.
Park Hill flats
, an example of 1950s and 1960s council housing estates in Sheffield
In the 1950s and 1960s, many of the city's slums were demolished, and replaced with housing schemes such as the Park Hill flats. Large parts of the city centre were also cleared to make way for a new system of roads. Increased automation and competition from abroad resulted in the closure of many steel mills. The 1980s saw the worst of this run-down of Sheffield's industries, along with those of many other areas of the UK. The building of the Meadowhall Centre on the site of a former steelworks in 1990 was a mixed blessing, creating much-needed jobs but hastening the decline of the city centre. Attempts to regenerate the city were kick-started when the city hosted the 1991 World Student Games, which saw the construction of new sporting facilities such as the Sheffield Arena, Don Valley Stadium and the Ponds Forge complex.
Sheffield is changing rapidly as new projects regenerate some of the more run-down parts of the city. One such, the Heart of the City Project, has initiated a number of public works in the city centre: the Peace Gardens were renovated in 1998, the Millennium Galleries opened in April 2001, the Winter Gardens were opened in May 2003, and a public space to link these two areas, the Millennium Square, was opened in May 2006. Additional developments included the remodelling of Sheaf Square, in front of the refurbished railway station. The square contains "The Cutting Edge", a sculpture designed by Si Applied Ltd and made from Sheffield steel.
Sheffield was particularly hard hit during the 2007 United Kingdom floods and the 2010 'Big Freeze'. Many landmark buildings such as Meadowhall and the Sheffield Wednesday ground flooded due to being close to rivers that flow through the city. In 2010, 5,000 properties in Sheffield were identified as still being at risk of flooding. In 2012 the city narrowly escaped another flood, despite extensive work by the Environment Agency to clear local river channels since the 2007 event. In 2014 Sheffield Council's cabinet approved plans to further reduce the possibility of flooding by adopting plans to increase water catchment on tributaries of the River Don.
Since 2012, there have been disputes between the city council and residents over the fate of the city's 36,000 highway trees, with 4,000 having been felled as part of a scheme to maintain the city streets. However, there have been plans for the highway maintenance to replant all felled trees across the city, including those historically felled and not previously replanted.