Until 1866 when it was made a separate civil parish, Hardwick was a township in the ancient parish of Torksey in the Parts of Lindsey in Lincolnshire. In 1894 it became part of Gainsborough Rural District.
GENUKI states that in 1881 Alexander HUNTER owned most of the land in Hardwick township.
Wikipedia redirects Hardwick to the civil parish of Kettlethorpe, but since neither A Vision of Britain through Time nor GENUKI mention this link it must be assumed that it occurred in 1974 or later. (A Vision of Britain through Time and GENUKI both cease their coverage with the alterations to local government that occurred in 1974.)
The civil parishes of Kettlethorpe, Hardwick, Fenton, Torksey and Newton on Trent are all located in the southwest corner of the former Gainsborough Rural District. To the west and south is the county of Nottinghamshire. Kettlethorpe is the most central of the parishes with Hardwick on the east, Fenton to the northwest and Newton on Trent to the southwest. Torksey is northwest of Hardwick. They all have low population densities and thus it has been economically viable to merge them given the improvements in communication over the past century.
Lincolnshire is very low-lying and land had to be drained for agriculture to be successful. The larger drainage channels, many of which are parallel to each other, became boundaries between parishes. Many parishes are long and thin for this reason.
There is much fenland in Lincolnshire, particularly in the Boston and Horncastle areas. Fenlands tended to be extraparochial before the mid 1850s, and although many sections were identified with names and given the title "civil parish", little information has been found about them. Many appear to be abolished in 1906, but the parish which adopts them is not given in A Vision of Britain through Time. Note the WR category Lincolnshire Fenland Settlements which is an attempt to organize them into one list.
From 1889 until 1974 Lincolnshire was divided into three administrative counties: Parts of Holland, Parts of Kesteven and Parts of Lindsey. These formal names do not fit with modern grammatical usage, but that is what they were, nonetheless. In 1974 the northern section of Lindsey, along with the East Riding of Yorkshire, became the short-lived county of Humberside. In 1996 Humberside was abolished and the area previously in Lincolnshire was made into the two "unitary authorities" of North Lincolnshire and North East Lincolnshire. The remainder of Lincolnshire was divided into "non-metropolitan districts" or "district municipalities" in 1974. Towns, villages and parishes are all listed under Lincolnshire, but the present-day districts are also given so that places in this large county can more easily be located and linked to their wider neighbourhoods. See the WR placepage Lincolnshire, England and the smaller divisions for further explanation.