Berkshire is an area south of the upper Thames, which separated the county from Oxfordshire and Buckinghamshire, flowing from Lechlade, via Oxford, Abingdon, Wallingford, Reading, Henley, Marlow, Maidenhead, to Windsor. The southern parts are drained by the Kennet, which flows through Hungerford and Newbury to join the Thames at Reading. Through the centre of the county run the chalk hills, from Uffington, via Wantage, to Streatley—the line of the Icknield Way and the Berkshire Ridgeway. There were therefore two east–west corridors—one north of the downs, one south.

In Roman times, the area was the territory of the Atrebates. From the early days of the Saxon occupation, it was disputed between Mercia and Wessex. Mercia gained the upper hand in the mid-7th cent. and the region was still held by Offa of Mercia in the 770s. It was recaptured by King Egbert for Wessex in the early 9th cent. and became an important part of the kingdom: Wantage was a royal estate and Alfred the Great was born there. It was probably one of the earliest shires to be organized and placed under an ealdorman: it was first mentioned by the Anglo-Saxon Chronicle under 860, when Æthelwulf, earldorman of Berkshire, fought against the Danes with the men of Hampshire. The name has caused difficulty. In the Chronicle it appears as Berrocscire, and Asser, Alfred's biographer, explained it as a wood, where box was abundant: this seems rather slight for a place-name. It was first in the diocese of Dorchester, just across the river in Oxfordshire, then in Winchester, and from 909 in Ramsbury in Wiltshire, whence it was finally transferred to the new diocese of Salisbury. This suggests that it was border country, lacking a powerful capital. A large monastery was established at Abingdon in 675 and, well before the Conquest, the crossing-points at Wallingford, Reading, and Windsor had grown into small towns. In 1066 William crossed the Thames at Wallingford on his triumphant march from Hastings. He took over many of the estates of the previous royal family and began building the castle at Windsor, soon established as a major royal residence. Its position astride some of the main routes to London gave Berkshire strategic importance. In the civil war between King Stephen and Matilda in the 12th cent., Wallingford castle was held for the latter and withstood repeated sieges. In John's reign, it was again held for the king against his barons, and in Henry III's reign was taken by Simon de Montfort before the battle of Lewes. During the 17th-cent. civil wars, the county was on the border between royalist and parliamentarian: Wallingford was held throughout the war for the king, Windsor for his opponents. The two battles of Newbury in 1643 and 1644 were fierce but inconclusive: Donnington castle held out for the king until the last month of the war.

Berkshire remained a quiet rural area, the downs feeding the sheep, and Newbury and Abingdon gaining reputations for cloth. The wealth of John Winchcombe, ‘Jack of Newbury’, in the early Tudor period was legendary and his exploits were commemorated in ballads and chapbooks. Reading's place on the river gave it steady prosperity: in the 1720s, Defoe found it ‘large and wealthy, the inhabitants rich and driving a very great trade’. But the extensive areas of downland and the barren, sandy heathland in the east kept the population down. The Kennet and Avon canal in the south, opened in 1810, gave a modest boost to trade, but the Wiltshire and Berkshire, a narrow canal completed in 1809, had desultory traffic from the beginning. The market towns of the shire remained small, until the great expansion of Reading itself—9,000 in 1801, 60,000 by 1901, 134,000 by 1991: Huntley and Palmer's biscuit partnership dates from 1841. Didcot grew considerably in the 20th cent. as a rail junction, but Wantage, Wallingford, and Faringdon, bypassed by the main lines, stayed small: Wallingford had a population of 2,800 in 1851 and 2,700 in 1901; Faringdon declined from 3,400 to 2,900; Wantage increased slowly from 3,000 to 3,700. Berkshire remained essentially a shire to be passed through, from east to west. Brunel's Great Western railway cut a large swathe through the north of the county in the 1830s by way of the valley of the White Horse, and the Taunton to Reading line, through Hungerford and Newbury, opened in 1847. The M4 motorway, completed in 1971, bisected the county from Bray in the east to Membury in the west. Many of the industries retained farming connections—brewing or horse-racing, with stables at Lambourn and East Ilsley, and important courses at Ascot and Newbury. Twentieth-cent. industries included atomic research at Harwell and Aldermaston. By the local government reorganization of 1972, the county gained Slough and Eton from Buckinghamshire, but lost Abingdon, Faringdon, Wantage, and Wallingford to Oxfordshire—Mercia's belated triumph. At the same time, the growth of Bracknell, one of the earliest post-war new towns, meant that the balance of the county population had tipped dramatically towards the east, succumbing to the pull of London.

After the Banham commission report of 1994 the county was abolished, save for ceremonial purposes, and replaced by six unitary authorities, Reading, Wokingham, Slough, Bracknell Forest, Windsor and Maidenhead, and West Berkshire (Newbury).

J. A. Cannon

Berkshire Former county in s central England, now split into six unitary authorities; the county town was Reading. Berkshire lies almost entirely within the River Thames basin, which marks the n border. The Berkshire Downs run across the county. It is an agricultural area; dairy cattle and poultry are important, and barley is the main crop. Industries: nuclear research. Area: 1255sq km (485sq mi). Pop. (1998) 788,422.