The castle of Monmouth was originally built by the Normans in the late 11th century, as one part of a system of fortifications to help establish their dominance of the Welsh Marches, and as a base for extending their control into Wales itself.

[1] The castle, which overlooked the confluence of the rivers Wye and Monnow in a strategically important border area, was initially a modest motte and bailey structure, rebuilt in stone by 1150.

[2] A small market town developed around the castle and, in 1267, it passed into the hands of Edmund Crouchback, Earl of Lancaster and son of Henry III.

[3] The 1297 grant was issued for five years and the funds collected allowed for the construction of the medieval town walls and gates.

[4] On 1 June 1315, again at Henry de Lancastre's request, the grant was renewed for another three years, indicating that the project was either incomplete or in need of repairs.

[12][16] By 1705, the Monnow Bridge Gatehouse was in need of maintenance, and the Monmouth Common Council ordered that it be repaired and upgraded.

The Monnow Bridge Gatehouse, part of the town walls and defences, is listed separately due to its particular interest.

Aside from the tower which is incorporated into the Old Nag's Head pub, there are no other surviving upstanding remains of the Monmouth town walls.

However, Monk's Gate, near the Priory, was removed in 1710; it is feasible that the curved wall at the Masonic Hall entrance indicates its previous location.

[4][22] An 1886 article in Archaeologia Cambrensis by William Bagnall-Oakeley, husband of antiquarian Mary Ellen Bagnall-Oakeley, discussed Monmouth and included an analysis of the 1610 map of Monmouth by cartographer John Speed, comparing it with the account of the circa 1538 visit by antiquarian John Leland, also Leyland.

[7] Instead, Bagnall-Oakeley referred to Speed's map which apparently demonstrated a town wall which ended at the top of Monnow Street, near the Bayley (bailey).

[7] Based on his examination of the area with another Monmouth resident and his reading of military accounts, the author speculated that there might have been an additional, sixth gate, lower down on Monnow Street, expressing some disagreement with both Leland and Speed.

[4][22] Aside from the Monnow Bridge Gatehouse which is given a separate listing as a scheduled monument due to its special interest, the only standing remnant of the Monmouth town walls and defences is the medieval Dixton Gate tower which was incorporated into the Old Nag's Head public house.

[21] In February 2012, proposed renovation of the building adjoining the medieval East Gate led to the recommendation of an archaeological field evaluation.

Therefore, while the Monnow Bridge and Gate were built mainly for defensive purposes, ultimately their primary function was financial; they were utilised to collect tolls.