Calne is on a small river, the Marden that rises 2 miles away in the Wessex Downs, the only town on that river, on a short branch of the Wilts & Berks Canal. It is on the A4 road national route 19 miles east of Bath, 6 miles east of Chippenham, 13 miles west of Marlborough and 16 miles southwest of Swindon. Wiltshire's county town of Trowbridge is 15 miles to the southwest, with London 82 miles due east as the crow flies. According to the 2011 Census, Calne had 17,274 inhabitants.
In AD 978 Anglo-Saxon Calne was the site of a large two-storey building with a hall on the first floor. It was here that St Dunstan, Archbishop of Canterbury met the Witenagemot to justify his controversial organisation of the national church, which involved the secular priests being replaced by Benedictine monks and the influence of landowners over churches on their lands being taken away. According to an account written about 1000, at one point in this meeting Dunstan called upon God to support his cause, at which point the floor collapsed killing most of his opponents, whilst Dunstan and his supporters were in the part that remained standing. This was claimed as a miracle by Dunstan's supporters.
In 1086 Calne may already have been, as it was later, a market town on the main London-Bristol road. The church in it was well endowed, 74 or more households in it were held almost outright by burghal tenure (as citizens of a borough), and the lordship of its large outlying land stood divided between the king, of whom 45 of the burgesses were tenants, and the church. In the Middle Ages the king's successor as the lord of Calne manor and, as owner of the church's revenues, the treasurer of Salisbury Cathedral each had the right to hold a market and a fair in the town, on a similar street pattern, with two triangular market places or fair grounds. A modest hospital was provided on a modest endowment from 1248 until it provided no accommodation in 1546 and was sold two years later by the Crown.
Calne had a significant woollen broadcloth industry in the 18th century, and evidence of this can be seen set around the triangular green, The Green, by the parish church, where 24 listed buildings remain, five at Grade II* including the Tounson almshouses for the neediest poor Georgian era clothiers' houses and nearby are some of the 20 original cloth mills along the Marden. St Mary's church was built to the immediate north by the generous donations of rich clothiers and wool merchants in the 15th century and is among a minority of medieval churches which are Grade I listed.
Houses of the 17th and 18th centuries have external walls of stone and timber-framed walls inside. Most of the stone is limestone rubble, laid with ashlar dressings in houses of higher quality; the walls of many houses were rendered smooth. Until the 19th century quarries beside the London road north-west and south-east of the town were "apparently" according to D.A. Crowley's county history of 2002, the main sources of stone for building.
A relic of 19th century lime, a kiln, exists in the grounds of St Mary's School. This solid marine deposition is chiefly one chemical, calcium carbonate, and is dug in nearby pits for its main use in cement and as fertiliser on acid ground.
Calne's former railway station opened in 1863, the terminus of its own branch line of the Great Western Railway running east from Chippenham, with one intermediate stop: Stanley Bridge Halt. The opening of Black Dog Halt in the early 20th century, provided insufficient demand to slow a progressive decline. The branch closed as a result of the Beeching Axe in September 1965, having suffered the ignominy of making the biggest loss per mile of any line in the country.
Subsequently, Calne's main industry other than being a small market town was the imposing Harris pork processing factory and provided employment directly and indirectly to many of the residents until the early 1980s - at its closure in 1983 for example it employed over 2000 people out of a town population of 10,000. It is said that the pork-curing industry developed because pigs reared in Ireland were landed at Bristol and then herded across England on drovers' roads to Smithfield, London, passing through Calne. The factory started in the second half of the 18th century when brothers John and Henry Harris started businesses which merged in 1888 as C. & T. Harris & Co. The factory has now been fully demolished and its site redeveloped as shops, housing and a library. As a result of the closure, unemployment in the town increased considerably and during much of the 1980s Calne suffered many of the economic restructuring problems more usually associated with large cities. A legacy to this day survives with gastronomic plaudits for the techniques developed.