The Victoria County History explains the shape of the town in one sentence: Thirsk lies between two important medieval highways which run along opposite banks of Cod Beck. On the east was the Street from York to the port of Yarm. On the west was the road from Topcliffe to Northallerton and Scotland. The town grew in between them, in two halves.
Old Thirsk, on the east bank, is the older settlement and was the borough. Its houses stand along Long Street and around St James’s Green, the great open space that was the “old market stead” named in 1398 and still held the cattle market in 1859. The fifty-two burgage tenements that carried the parliamentary vote were all here.
New Thirsk, on the west bank, grew up around the bailey of the castle. That is where the Market Place is, and the Market Place contains no burgages at all, which is how you know it is the later of the two. The bit visitors find confusing, that the market square is in the newer half of the town, is exactly the interesting part. Sowerby and Norby were separate places again, and have since grown into the whole.
In 1086 Domesday recorded Thirsk as Tresche, from an Old Scandinavian word meaning fen or lake. Hugh son of Baldric’s manor, with ten villans and eight acres of meadow, was worth four pounds in 1066 and ten shillings in 1086. That collapse is the Harrying of the North showing up in the accounts, and it is the most eloquent number in the town’s early record.