The name "Cleethorpes" is thought to come from joining the words "clee", an old word for clay, and "thorpes", an Old English/Old Norse word for villages, and is of comparatively modern origin. Before becoming a unified town, Cleethorpes was made up of three small villages, or "thorpes": Itterby, Oole and Thrunscoe, which were part of a wider parish called Clee (not to be confused with Old Clee).
While there are neolithic and Bronze Age remains in the area, permanent occupation appears to date from the 6th century, when the Danes arrived, with substantial communities only appearing in the 9th century.
The manor of Itterby was purchased in 1616 by the trustees of Peter Blundell's charity for the benefit of scholars and fellows at Sidney Sussex College, Cambridge from Blundell's School, Tiverton. This is reflected in many of the street and park names in the area.
Cleethorpes developed as a fishing village. By the time of the 1801 census the population was 284. The 1820s saw the first developments of Cleethorpes as a health holiday resort, with sea-bathing and the taking of medicinal waters becoming fashionable. By 1831 the population had increased to 497.
In 1842 the Cleethorpes Enclosure Bill was enacted. of land were divided between land owners and eight new roads developed. In 1848 Cleethorpes was described as
The resort expanded following the linking of the town by railway with the industrial towns of Yorkshire. Cleethorpes Pier opened in 1873, and the promenade in 1885. Cleethorpes with Thrunscoe was constituted a Local Board of Health District in 1873, and under the Local Government Act of 1894 it became an urban district.
In 1916 the urban district was renamed Cleethorpes, and in 1922 and 1927 the town's boundaries were extended to include part of Humberston (as far as North Sea Lane) and the Beacon Hill area of Weelsby parish. In 1936 Cleethorpes was granted a charter of incorporation to become a municipal borough.
On 22 September 1956 at 3pm a UFO was spotted for over an hour off the Cleethorpes coast; it was seen by radar at RAF Manby too. It was a large spherical object with a glass appearance. The Lakenheath-Bentwaters incident had happened the month before.
Uniting Cleethorpes and Grimsby
Cleethorpes successfully resisted attempts by Grimsby to absorb it and in 1974 it became the Borough of Cleethorpes within the new county of Humberside. However when Humberside County Council was abolished in 1996, Cleethorpes Borough Council was joined with Grimsby Borough Council as the unitary authority of North East Lincolnshire. In 2009, North East Lincolnshire Council agreed to market the towns of Grimsby, Immingham and Cleethorpes, under the Greater Grimsby banner.