The county contains a curiously large number of abandoned settlements, which K.Rutherford Davis attributes to a mixture of poor harvests on soil hard to farm, and the Black Death which ravaged Hertfordshire starting in 1349.Their main settlement (or oppidum) was Verlamion on the River Ver (near present-day St Albans).
Hatfield in Hertfordshire has seen two rail crashes of international importance (in 18).
Though nowadays Hertfordshire tends to be politically conservative, historically it was the site of a number of uprisings against the Crown, particularly in the First Barons' War, the Peasants' Revolt, the Wars of the Roses and the English Civil War.
At that time, in the war between Saxon and Norseman, Hertfordshire was on the front line.
When, after the Saxon victory in the Battle of Ethandun in 878, the Saxon King Alfred the Great and Norse King Guthrum the Old agreed to partition England between them, the dividing line between their territories split what was to become Hertfordshire almost through the middle, along the line of the River Lea and then along Watling Street.
There is considerable evidence of a mint in Hertford at this period.