market town and historic fortress, historic and present county of Monmouthshire (Sir Fynwy), Wales, on the west bank of the River Wye where it forms the border between England and Wales, near its confluence with the River Severn. Situated at a strategic point in the Wye valley, Chepstow was a site of fortifications in prehistoric, Roman, and Saxon times. These efforts culminated in the great 12th-century Norman castle that was constructed on a spur of rock overlooking the river and the old Roman road to South Wales. The town grew up around the castle during the 14th and 15th centuries and was granted a charter in 1524. Parts of the ancient town walls are still visible, and the impressive 16th-century town gate houses a small museum. Chepstow was active as a port until the 19th century, when larger vessels were handicapped by the shallow draft and narrowness of the channel. The town's economy now rests mainly on engineering and providing services for the surrounding agricultural area. Tintern Abbey, a Cistercian abbey now in ruins, made famous by the English poet William Wordsworth, lies 4 miles (6 km) north. Pop. (2001) 10,821.