Monmouthshire is one of thirteen historic counties of Wales and a former administrative county. It corresponds approximately to the present areas of Monmouthshire, Blaenau Gwent, Newport and Torfaen, and the parts of Caerphilly and Cardiff east of the Rhymney River.

The eastern part of the county is mainly agricultural, while the western valleys had rich mineral resources. This led to the area becoming highly industrialised with coal mining and iron working being major employers from the 18th century to the late 20th century. The five largest towns are Newport, Cwmbran, Pontypool, Ebbw Vale and Abergavenny.

Between about the 5th and 10th centuries the Welsh Kingdom of Gwent covered a variable area roughly contiguous with Monmouthshire. It then became part of Morgannwg, and was part of the unified Welsh realm of Gruffydd ap Llywelyn. At the time of the Domesday Survey in 1086 the Chepstow and Monmouth areas were, for accounting purposes, reckoned as parts of the English counties of Gloucestershire and Herefordshire respectively.

The ‘county or shire of Monmouth’ was formed from parts of the Welsh Marches by the Laws in Wales Act 1535. The county encompassed the towns of Monmouth, Chepstow, Caerleon, Newport, Usk, Raglan and Abergavenny. The Act also designated Monmouth as the ‘Head and Shire town of the said county or shire of Monmouth’’, and ordered that the Sheriff’s county or shire court be held alternately in Monmouth and Newport. Monmouthshire’s status was somewhat ambiguous between 1542 and 1974, with it considered by some as part of England and by others as part of Wales.

In the late 17th century, under Charles II, Monmouthshire was added to the Oxford circuit of the English Assizes.

The eastern part of the county is mainly agricultural; wheat and rye were the chief crops produced in the fertile valleys of the Usk; oats and barley were grown in the uplands. The while the western valleys had rich mineral resources. This led to the area becoming highly industrialised with coal mining across more than 100 mines and iron working being major employers from the 18th century to the late 20th century.

Surnames with a particular association with Monmouthshire in the late 19th century included Rosser, Prosser, Edmunds, Watkins, Howells, Bevan, Morgan, Meredith, Jenkins and Lewis.

Records for Monmouth are held at Gwent Archives in Ebbw Vale, gwentarchives.gov.uk; for other resources see heritagehunter.co.uk .