The Parliamentary Constituency of Hitchin & Harpenden was created in 1995 as a result of the Boundary Review.

The constituency is made up of:

• Hitchin and the surrounding villages (Pirton, Holwell, Ickleford, Offley, Lilley, Hexton, St Paul's Walden, King's Walden, St Ippolyts, Breachwood Green, Preston, Little & Great Wymondley, Langley, Kimpton and Whitwell), which were formerly part of the North Hertfordshire constituency. Chesfield Ward became part of the constituency in 2010.
• Harpenden and the villages of Redbourn and Sandridge which were originally part of St Albans constituency.
• Wheathampstead which came from the Welwyn and Hatfield constituency.

Hitchin is an historic market town; whereas Harpenden has only expanded from a small village over the last couple of centuries.