Devizes Castle was built in 1080. Because the castle was on the boundaries of the manors of Rowde, Bishops Cannings and Potterne it became known as the "castrum ad divisas" - or the castle at the boundaries - from where the name Devizes came. On early maps the town's name is shown as The Devyses.
During the 12th and 13th centuries the town developed outside the castle with craftsmen and traders setting up businesses to serve the residents . The first known market in Devizes was in 1228. The main products in the 16th and early 17th centuries were wheat, wool and yarn, with cheese, bacon and butter increasing in importance later. Devizes also became known for its textiles.
In the early 18th century Devizes held the largest corn market in the West Country, trading in hops, cattle, horses and various cloth. Before the Corn Exchange was built in 1857 wheat and barley was bought and sold in the open, with sacks piled around the market cross. Wool merchants were able to build prosperous town houses in St. John's and Long Street and around the market place. From the end of the 18th century the manufacture of textiles declined, but other trades in the town included clock making, a bell foundry, booksellers, milliners, grocers and silversmiths. In the 18th century brewing, curing of tobacco and snuff-making were established in the town.
An inscription on the market cross records that:
"On Thursday the 25th of January 1753, Ruth Pierce of Potterne in this County, agreed with three other women to buy a sack of wheat in the market, each paying her due proportion towards the same. One of these women, in collecting the several quotas of money, discovered a deficiency, and demanded of Ruth Pierce the sum which was wanting to make good the amount. Ruth Pierce protested that she had paid her share, and said, ‘She wished she might drop down dead if she had not.’ She rashly repeated this awful wish; when to the consternation and terror of the surrounding multitude, she instantly fell down and expired, having the money concealed in her hand"
The coroner recorded that she had been "struck down dead by the vengeance of God."