The constituency was established as a Division of Hertfordshire by the Representation of the People Act 1918, largely created from the northern half of the Watford Division, including Hemel Hempstead, Berkhamsted and Tring. It also included north-western part of the St Albans Division, around Harpenden. Harpenden was transferred back to St Albans in 1974 and the constituency was temporarily abolished from 1983 to 1997 during which time it was replaced by West Hertfordshire.
Boundaries and boundary changes
1918–1950: The Municipal Borough of Hemel Hempstead, the Urban Districts of Berkhamsted, Harpenden, and Tring, the Rural Districts of Berkhamsted and Hemel Hempstead, in the Rural District of St Albans the parishes of Harpenden Rural, Redbourn, and Wheathampstead, and in the Rural District of Watford the parishes of Abbots Langley and Sarratt. 1950–1974: The Municipal Borough of Hemel Hempstead, the Urban Districts of Berkhamsted, Harpenden, and Tring, the Rural Districts of Berkhamsted and Hemel Hempstead, and in the Rural District of St Albans the parishes of Harpenden Rural and Redbourn. Parish of Wheathampstead transferred back to St Albans. Parishes of Abbots Langley and Sarratt included in the new County Constituency of South West Hertfordshire. 1974–1983: The Municipal Borough of Hemel Hempstead, the Urban Districts of Berkhamsted and Tring, and the Rural Districts of Berkhamsted and Hemel Hempstead. The Urban District of Harpenden and the part of the Rural District of St Albans now transferred back to St Albans. The constituency was abolished for the 1983 general election. Berkhamsted and the area to the south of Hemel Hempstead, including Kings Langley, was transferred to South West Hertfordshire. The remainder, including Hemel Hempstead and Tring, formed the new County Constituency of West Hertfordshire. 1997–2010: The District of Dacorum wards of Adeyfield East, Adeyfield West, Ashridge, Bennetts End, Boxmoor, Central, Chaulden, Crabtree, Cupid Green, Flamstead and Markyate, Gadebridge, Grove Hill, Highfield, Kings Langley, Leverstock Green, Nash Mills, South, and Warners End. Re-established for the 1997 general election from the bulk of the abolished County Constituency of West Hertfordshire. Kings Langley transferred back from South West Hertfordshire. 2010–present: The District of Dacorum wards of Adeyfield East, Adeyfield West, Apsley, Ashridge, Bennetts End, Boxmoor, Chaulden and Shrubhill, Corner Hall, Gadebridge, Grove Hill, Hemel Hempstead Central, Highfield and St Paul's, Kings Langley, Leverstock Green, Nash Mills, Warners End, Watling, and Woodhall. Minor loss to South West Hertfordshire following revision of local authority wards.
General Election 1939/40: Another general election was required to take place before the end of 1940. The political parties had been making preparations for an election to take place from 1939 and by the end of this year, the following candidates had been selected;
