THIRSK, a market-town in the North Riding of Yorkshire, is situated on the North Eastern Railway, and on the Codbeck, a branch of the Swale, 21 miles south of Darlington, 11 north-east of Ripon, and 210 north of London. The Codbeck is crossed by two stone bridges connecting the old and the new town. The church of St Mary, in the Perpendicular style, with parvise, chancel, nave, aisles, porch, and tower 80 feet in height, is the noblest church in the Riding. The chancel was repaired in 1844, and the whole building restored in 1877. The moat of the ancient castle built by the Mowbrays about 980 still remains. The principal modern buildings are the assembly rooms (1849), the mechanics' institute (1852), and the new court-house (1886). Standing in the fertile district of the Vale of Mowbray, the town has an extensive home and foreign agricultural implement trade. Iron-founding, engineering, tanning, and brickmaking are carried on, and there are large flour-mills. The population of the parliamentary borough, now disfranchised (area 11,828 acres), in 1871 was 5734, and in 1881 it was 6312. The population of the township in 1881 was 3337.
Thirsk owes its origin to the castle of the Mowbrays, and here Roger de Mowbray erected his standard, in conjunction with the king of Scotland, against Henry II. Upon the suppression of the revolt the castle was destroyed. In the reign of Henry VII., Henry Percy, earl of Northumberland, is said to have been put to death beneath an elm tree which formerly grew on St James's Green. Thirsk was a borough by prescription, but was never incorporated. It first returned members to parliament in the reign of Edward I., but not again till the last parliament of Edward VI. In 1832 the number of representatives was reduced to one, and in 1885 it ceased to be separately represented.