Antonine Wall

Construction began around AD 142 on the order of the emperor Antoninus Pius, who, unlike his predecessor Hadrian, never set foot in Britain; pressure from the Caledonians probably lay behind his decision to push the empire's troops farther north. Quintus Lollius Urbicus, then governor of Roman Britain, supervised the work; estimates of how long it took vary widely, with six and twelve years most often proposed. It ran 63 kilometres (39 miles) from Old Kilpatrick on the Firth of Clyde to Carriden near Bo'ness on the Firth of Forth, intended to supersede Hadrian's Wall, 160 kilometres south, as the frontier of Britannia. While it was garrisoned it was the northernmost frontier barrier of the Roman Empire.

The barrier was a bank of layered turves on stone foundations, about three metres (10 feet) high, with a deep ditch on the northern side and a road, the Military Way, running behind it to the south; a wooden palisade is thought to have topped the turf. The Romans planted forts and camps north of the line, but never conquered the Caledonians, and the wall suffered many attacks.

The first forts' stone foundations and wing walls show that a stone wall on Hadrian's model was originally intended, a plan quickly amended. Forts were at first to stand every 10 kilometres, soon revised to every 3.3 kilometres, giving nineteen forts, with at least nine smaller fortlets, some later replaced by forts. Rough Castle is the best preserved and among the smallest of the forts, and Kinneil near Bo'ness the most visible fortlet.

The soldiers who built the wall commemorated the construction and their struggles with the Caledonians on decorative slabs, twenty of which survive. These distance stones, embedded in the wall to mark the length each legion had built, are unique to the Antonine Wall; research at Glasgow University has shown they were once brightly painted rather than bare as they now appear. They are kept in the university's Hunterian Museum and are said to be the best-preserved statuary from any Roman frontier.

The legions withdrew south to Hadrian's Wall in 162, within two decades of the wall's completion; the Romans may in time have reached an accommodation with the Brythonic tribes between Forth and Clyde, perhaps fostering them as buffer states later remembered as the Old North. After a series of attacks in 197, the emperor Septimius Severus arrived in Scotland in 208 and campaigned against the Maeatae and the Caledonians beyond them. He carried out substantial work on Hadrian's Wall, but there is no evidence the Antonine Wall's remains received any attention during the campaigns of 208-210.

Writing in 730 and following Gildas, Bede wrongly ascribed the wall to the Britons, describing a rampart raised "not of stone ... but of sods", running from near the monastery of Abercorn west to Dumbarton. References in late Roman sources to Severus's wall-building led later scholars, Bede among them, to mistake the Antonine Wall for Hadrian's.

Medieval chroniclers knew it as Gryme's dyke; John of Fordun took the name from the grandfather of the imaginary king Eugenius son of Farquahar. It became Graham's dyke, a name still found at Bo'ness, and was then linked with Clan Graham. Hector Boece's History of Scotland of 1527 called it the wall of Abercorn and repeated the story that Graham had destroyed it.

Renaissance patrons began to collect antiquities: George Keith, 5th Earl Marischal, set a slab from the wall into the walls of Dunnottar Castle and had it painted and gilded; it is now in the Hunterian. Arthur's O'on at Stenhousemuir, a domed Roman rotunda that may have been a temple or a victory monument, was demolished for its stone in 1743, and a replica stands at Penicuik House.

The first capable attempt to map the wall systematically was made in 1764 by William Roy, forerunner of the Ordnance Survey, whose drawings are now the only reliable record of the stretches later destroyed by development. Sir George Macdonald's study of 1911, expanded in 1934, underpinned an Ordnance Survey folio of 1931, and the Survey resurveyed the whole line in 1979-80.

The United Kingdom's nomination for World Heritage status was announced in 2003 and backed by the Scottish Government from 2005; on 7 July 2008 the Antonine Wall was listed as an extension of the Frontiers of the Roman Empire World Heritage Site. Several individual sites along the line are in the care of Historic Environment Scotland, all of them unmanned and open at all reasonable times.