The name of Reigate does not appear in the records until the 12th century, by which time a settlement had grown up in the shadow of the castle first built by the Earls of Surrey soon after 1088. Reigate Castle saw very little by way military activity. It was captured without a fight by Louis, the Dauphin of France, in 1216, and was temporarily occupied by Royalist forces during the Second Civil War in 1648. Thereafter it was left to decay and was described as 'ruinous' in 1686. All that survives of the castle today are the motte and bailey earthworks adorned with an 18th century mock gatehouse. Much of the hill on which the castle stood is riddled with tunnels dug over the centuries to mine silver sand.

If Reigate had a centre of any sort in the Saxon period it was probably some distance east of the present High Street around the parish church of St Mary Magdalene. The Domesday Survey of 1086 identifies this original settlement as 'Cherchefelle' and in later documents it is referred to as 'Crichefeld', meaning 'open space marked by a barrow'. Domesday records that it was held by King William and had two mills, which were almost certainly on the River Mole, but the church is not mentioned, although one probably already existed. The present church has features dating back to about 1200.

Reigate had a market by 1276 and was recognised as a borough in 1291. The market was important to the future development of the town and in 1610 Reigate was reported to be one of the top four market towns in Surrey. Trade at the Tuesday market was chiefly in wheat. In 1679 Charles II granted an extra monthly market and also an annual cattle fair to be held on the Wednesday of Easter week. The Market House, built about 1728, is still a prominent feature of the High Street.

In 1841 the railway line from London to Brighton was opened but it bypassed Reigate. The town's station dates from 1849 and was built on the cross-country route running west to Guildford, via Dorking. This line met the Brighton line in a sparsely populated area east of Reigate and then continued on into Kent. It was at this major junction that the town of Redhill grew up and in 1870 a fortnightly stock and corn market was opened in the new town. This spelt the end of Reigate as a market town. However, the railway brought new residents to Reigate and town began to develop as an attractive place in which to live.