Hertfordshire, though a small county, has little geographical unity. The southern parts are within the orbit of London and discharge commuters into Euston, St Pancras, King's Cross, and Liverpool Street. The north retains quiet spots like Gaddesden in the west and Wyddial in the east. The magnetic attraction of London has meant that, since Roman times, communications have run north–south, with Akeman Street, Watling Street, and Ermine Street as the main thoroughfares. East–west communications have always been difficult. The Icknield Way, the great pre-Roman route, is too far north to unite the shire. Even today it is doubtful how often people from Tring find themselves in Bishop's Stortford, save to play football.

The divisions within the county run deep within its natural and political history. It consists of two river basins, with the natural watershed forming the northern boundary. The Lea rises just outside the county near Luton and leaves it in the south-east to join the Thames near Blackwall Tunnel: with its tributaries the Mimram, Beane, Rib, Ash, and Stort, it drains the eastern half. The western parts drain into the Ver, Colne, Chess, and Gade, which meet near Watford and join the Thames at Staines. The north-west of the county, adjoining the Chilterns, is gentle, wooded chalk country; the north-east is downland and bare wide fields; the south-east is flat clay, running down to desolate marshes at Cheshunt, bordering Essex.

In the immediate pre-Roman period, the area was part of the territory of the Catuvellauni, whose chief, Cassivellaunus, opposed Caesar's expeditions. His grandson Cunobelinus seems to have moved his capital from Verulamium, near St Albans, to Colchester, ruling over the Trinovantes. Caratacus, his son, led a protracted resistance to the Roman invasion of ad 43, was driven west, captured, and died a prisoner in Rome. The area was soon brought under Roman control, but Colchester, Verulamium, and London were all sacked during Boudicca's revolt of ad 61. Braughing is on the site of a Roman settlement of some importance.

The area was one of the earliest to be occupied by the Saxons and formed at first part of the diocese of London, established in the early 7th cent. to minister to the East Saxons. There was subsequently an ecclesiastical reorganization since, until the foundation of the new diocese of St Albans in 1877, most of Hertfordshire was in the vast diocese of Lincoln, only the eastern part staying with London. In the 8th cent. the region formed part of the kingdom of Mercia, and Offa is said to have died in 796 while building the great abbey on the site of St Alban's martyrdom. In the 9th and 10th cents., Danes and Saxons fought for control. The boundary between the territories of Alfred of Wessex and Guthrum was settled by the treaty of Wedmore in 878 as the line of the river Lea. The truce was temporary, for in 896 the Danes are reported to have sailed up the Lea to near Ware and to have been stranded when Alfred ordered ditches to be dug to drain the stream. Edward the Elder, in his counter-attack in 913, fortified Hertford as a strong point and it became the nucleus of the emerging county. The first reference to Hertfordshire by name is in the Anglo-Saxon Chronicle for ad 1011 and by the time of the Domesday survey it had been divided up into 8½ hundreds. In the 13th cent. Hertford and St Albans established their right to parliamentary representation and were joined, on and off, by Bishop's Stortford and Berkhamsted. In 1586 Camden admired the county enormously: it was ‘well furnished with corn-fields, pasture-ground, meadows, little woods and small, but very clear, streams’. Hertford, slightly off centre, never dominated the shire as some county towns did, and a considerable number of small market towns grew up, serving their immediate locality—Ashwell, Buntingford, Royston, Baldock, Hitchin, and Hoddesdon. St Albans was always bigger than Hertford and when the first county council was set up in 1889, it met alternately in the two towns.

The modern history of Hertfordshire is one of slow encroachment by London, Cobbett's ‘Great Wen’. The pull of London had been felt from the earliest days, particularly in the south-east, where the river Lea gave easy access to east London. Efforts to improve the river began centuries before the river Lea navigation was completed. Competition was fierce. Neighbours, who depended on sending corn and malt to London by cart, smashed banks and destroyed locks on the river, as well as hinting that barge cargoes picked up moisture and weighed heavily. Hertford and Ware had a long-standing feud, with the Ware men stringing barges across the river to stop Hertford traffic. In the west of the county, the opening in 1800 of the Grand Junction canal, through Tring and Rickmansworth, assisted the growth of industry, especially paper-making and printing. Yet despite these developments, the county remained rural until late. There were plenty of open fields surviving well into Victoria's reign, estates in the county were much sought after by gentlemen with business in London, and tributes to the beauty of the shire continued to pour in. Charles Lamb, in a famous essay, sang the delights of ‘Mackerye End in Hertfordshire’. In 1801 no town in the county had as many as 4,000 inhabitants. By 1851, though Hertford had scarcely grown at all, St Albans was over 8,000, Hitchin and Hemel Hempstead over 7,000, and Watford over 6,000.

But by 1901 the shape of the 20th cent. was becoming clear. Watford had increased to 32,000, twice the size of the next town, St Albans; and Cheshunt (12,000) and Barnet (7,000), on the fringes of London, had moved up. Two years later, a development which cast a long shadow, took place. The first garden city was started on a 4,000-acre site at Letchworth, chosen in the main for its nearness to London. It was joined after the First World War by the second garden city at Welwyn. In the first half of the 20th cent. the county population increase was five times the national average. The success of the garden cities prompted governments to look to Hertfordshire for sites for the new towns. Stevenage was the first to be set up after the Second World War, followed by Hatfield and Hemel Hempstead, and Welwyn was taken over as a new town. Whatever the merits of new towns as such, the effect upon a small county of five in such close proximity was predictable. Increasingly it is reduced to quiet pockets and enclaves. Within the network of motorways and junctions, fragments of an old county survive. But few of the motorists using the M25 between junctions 24 and 25 have time to reflect that, beneath them, is the estate of Theobalds, where James I once nearly drowned in Sir Hugh Myddleton's New River. In the local government reorganization of the 1990s, Hertfordshire retained its county status.

J. A. Cannon

Hertfordshire County in London's ‘commuter belt’, se England; the county town is Hertford. Other major towns include St Albans (built on the site of a Roman settlement), Watford, Hatfield, and Letchworth (Britain's first garden city). The terrain is flat, apart from an extension of the Chiltern Hills in the nw. The main rivers are the Lea, Stort, and Colne. Agriculture is important. Industries: engineering, electrical equipment, printing. Area: 1636 sq km (631sq mi). Pop. (1994) 1,005,400.