The earliest notice of Gainsborough, or Gainsburgh, was during the Saxon era. During this unsettled and war-like period it was the scene of various battles, sometimes forming part of the Kingdom of Northumbria, and at others being part of Mercia. Gainsborough's position on the banks of the river Trent made it very much a frontier town,and when Sweyne (Forkbeard) King of Denmark brought his vessels up the Trent in 1013 and landed his forces in the town, the whole of Northumbria, together with Lindsey, submitted to his rule.

Sweyne died the following year at Gainsborough. His son Canute, better known of tide turning fame, worked hard to consolidate his father's conquests, but the Danes were eventually defeated by the Saxons, led by Ethelred. At this period the Danes greatly outnumbered the English.

Although the Domesday Survey of 1086 recorded only eighty people living in Gainsborough, the town grew, and during the Middle Ages emerged as a major wool centre with a thriving port until the advent of the railways in 1849.

In the early part of the reign of Charles1, the town was important enough to be placed under the government of the Earl of Kingston. On 20th July 1643 Lord Willoughby of Parham, a Puritan, captured the town and imprisoned the Governor.

The Parliamentarians did not remain in Gainsborough for long, as the Marquis of Newcastle arrived shortly after with a large body of troops and forced them to surrender.

However, eight days later, Oliver Cromwell on his way to York routed the Royal forces when General Cavendish, their commander, and Colonel Markham of Allerton, were killed in the conflict.

A monument to this battle can be seen today on Foxby Hill, the scene of the battle. Although by no means a major Civil War battle, it was one of Cromwell's earliest field engagements in which his strategic excellence was recognised.

The town steadily grew during the 17th century. Gainsborough achieved the status of a port in 1841, and seven years later a Danish Vice-Consul had taken up residence in the town.

This company together with that of William Rose, vied with each other to employ the engineering talents of the local people. William Rose was the inventor of the first packaging machine and a plaque commemorating this achievement can be seen in the town centre.

Earlier timber framed buildings have been replaced by the red brick that characterises the town today. Only the Old Hall survives from that age of timber.