There is some evidence of a Roman villa, with possible British Iron Age antecedents. There are also remains of a late Roman temple on Portskewett Hill, and many coins of the 3rd and 4th centuries have been found.
Early Welsh history
The name Portskewett is generally believed to derive from the Welsh Porth-is-Coed, meaning "the harbour below the wood", or alternatively "the harbour of the area below the wood" - that is, the post-Roman cantref of Gwent Is Coed, centred on Caerwent about 3 miles away. An alternative derivation is from Porth Ysgewydd, the port of the elder wood.
According to tradition, in about the 6th century Caradog Freichfras, king of Gwent, moved his llys or court from Caerwent to Portskewett, where there was a strongly flowing fresh water spring which only dried up later when the Severn Tunnel was built. Alternatively, the court may have been based at nearby Sudbrook.
Portskewett is mentioned in ancient Welsh stories as one of the three chief ports of Wales. A Welsh poem of around the 7th century, Moliant Cadwallon, describes it as 1"beautiful Porth Esgewin, the estuary on the border", and the medieval Welsh phrase meaning from one end of the country to another translates as "from Porth Wygyr to Portskewett".
The harbour later silted up. It is now a marshy area at Caldicot Pill, close to the Second Severn Crossing and industrial sites, and crossed by power cables and railway lines, including the entrance to the Severn Tunnel. Archaeological investigations have revealed wetland structures, including fish traps, with dates from the 6th century onwards.
After the Norman conquest the area became a "hardwick" or cattle ranch. The village church is dedicated to St Mary. The original parts of the church date back to the late 11th century and are made of local limestone; the carved crosses on the blocked up back doorway could be even older. The church has been restored and altered on a number of occasions. The small windows in the upper part of the tower, for example, are typical of the 16th century. In the corner of the churchyard can be seen the steps which formed the base of a medieval churchyard cross.
From Norman times until 1919, the village was part of the St. Pierre estate, and was held by the Lewis family of St. Pierre. It declined in importance after the Norman period and for many centuries it was an agricultural village of no distinction, although it does appear that some iron mining continued near the village until at least the 17th century. In 1662 Thomas Lewis of St. Pierre, lord of the manor, granted the right to mine iron in the manor to Henry Rumsey.
By the 19th century the village was in decline. Between 1801 and 1861 the population of the parish, which includes Sudbrook, fell from 216 to 175. However, it expanded rapidly later in the 19th century, as housing was built for workers on the Severn Tunnel and with industrial development at nearby Caldicot. At the turn of the 20th century the population was some 900, steadily rising to about 1,300 by the 1970s. The village lost its railway station (on the Newport to Gloucester line) when it was closed under the Beeching Axe in 1964.