It borders Bedfordshire to the north-west, Cambridgeshire to the north-east, Essex to the east, Greater London to the south and Buckinghamshire to the west.

The county centres on the headwaters and upper valleys of the rivers Lea and the Colne; both flow south and each is accompanied by a canal.

The county's landmarks span many centuries, ranging from the Six Hills in Stevenage built by local inhabitants during the Roman period, to Leavesden Film Studios.

The volume of intact medieval and Tudor buildings surpasses London, in places in well-preserved conservation areas, especially in St Albans, which includes remains of the Roman town of Verulamium.

Many of the names of the current settlements date back to the Anglo-Saxon period, with many featuring standard placename suffixes attributed to the Anglo-Saxons: "ford", "ton", "den", "bourn", "ley", "stead", "ing", "lett", "wood", and "worth", are represented in this county by Hertford, Royston, Harpenden, Redbourn, Cuffley, Wheathampstead, Tring, Radlett, Borehamwood and Rickmansworth.

This relatively short-lived kingdom collapsed in the 9th century, ceding the territory of Hertfordshire to the control of the West Anglians of Mercia.

King Edward the Elder, in his reconquest of Norse-held lands in what was to become England, established a "burh" or fort in Hertford, which was to curb Norse activities in the area.

His father, King Alfred the Great, established the River Lea as a boundary between his kingdom and that of the Norse lord Guthrum, with the north and eastern parts of the county being within the Danelaw.

A century later, William of Normandy received the surrender of some senior English Lords and Clergy at Berkhamsted, before entering London unopposed and being crowned at Westminster.

Hertfordshire was used for some of the new Norman castles at Bishop's Stortford, and at King's Langley, a staging post between London and the royal residence of Berkhamsted.

Tring and Danais became one—Dacorum—from Danis Corum or Danish rule harking back to a Viking not Saxon past.

In Tudor times, Hatfield House was often frequented by Queen Elizabeth I. Stuart King James I used the locale for hunting and facilitated the construction of a waterway, the New River, supplying drinking water to London.

As London grew, Hertfordshire became conveniently close to the English capital; much of the area was owned by the nobility and aristocracy, this patronage helped to boost the local economy.

On 10 May 2002, seven people died in the fourth of the Potters Bar rail accidents; the train was travelling at high speed when it derailed and flipped into the air when one of the carriages slid along the platform where it came to rest.

The highest point in the county is at 244 m (801 ft) (AOD) on the Ridgeway long distance national path, on the border of Hastoe near Tring with Drayton Beauchamp, Buckinghamshire.

[13] At the 2011 census, among the county's ten districts, East Hertfordshire had the lowest population density (290 people per km2) and Watford the highest (4210 per km2).

Many of the county's major settlements are in the central, northern and southern areas, such as Watford, Hemel Hempstead, Kings Langley, Rickmansworth, St. Albans, Harpenden, Redbourn, Radlett, Borehamwood, Potters Bar, Stevenage, Hatfield, Welwyn and Welwyn Garden City, Hitchin, Letchworth and Baldock.

The physical geography of eastern Hertfordshire is less elevated than the far west, but with lower rising hills and prominent rivers such as the Stort.

The most important formations are the Cretaceous Chalk, exposed as the high ground in the north and west of the county, forming the Chiltern Hills and the younger Palaeocene, Reading Beds and Eocene, London Clay which occupy the remaining southern part.

The eastern half of the county was covered by glaciers during the Ice Age and has a superficial layer of glacial boulder clays.

[15] These range from beech woods of the Chilterns, clayland buffer zone countryside of Braughing and the Hadhams across to ancient hornbeam coppices west of the upper Lea valley.

The mining of chalk since the early 18th century has left unrecorded underground galleries that occasionally collapse unexpectedly and endanger buildings.

A product, now largely defunct, was watercress, based in Hemel Hempstead and Berkhamsted supported by reliable, clean chalk rivers.

[18] This is a table of trends of regional gross value added of Hertfordshire at current basic prices with figures in millions of British Pounds Sterling.

It is also the UK base of multi-nationals Hilton Worldwide, TotalEnergies, TK Maxx, Costco, JJ Kavanagh and Sons, Vinci and Beko.

Local newspapers in the county are: Waltham Cross, Broxbourne, is the location of the Lee Valley White Water Centre, a purpose-built venue opened in 2010 for the 2012 Summer Olympics.

[25] Stevenage was the first club to win a competitive match at the new Wembley Stadium, beating Kidderminster Harriers 3–2 in the 2007 FA Trophy Final.

[27] Arsenal, whilst based at the Emirates Stadium in the London Borough of Islington, has long held a training ground in the county.

The highest placed are Boreham Wood, Hemel Hempstead Town and St Albans City, who all play in the National League South, the sixth tier of English football.

Hertfordshire is the location of Jack Worthing's country house in Oscar Wilde's play The Importance of Being Earnest.