ArcGIS shapefile of 288 polygons providing boundary and attribute data for the fifty-five ancient counties of England and Wales as given in the 1831 census for England and Wales. As such this represents the counties of England and Wales as they were before the boundary changes caused by the Counties (Detached Parts) Act, 1844 (7 & 8 Vict. c. 61) which led to the elimination of some of the detached portions of counties.These data were created as part of a research program directed by Leigh Shaw-Taylor and Tony Wrigley, which aims ultimately to reconstruct the evolution of the occupational structure of Britain from the late medieval period down to the early twentieth century.

These data derive from the 173 digital maps of the boundaries of English and Welsh parishes and their subdivisions produced by Roger Kain and Richard Oliver based on the listing in the 1851 census. The maps were subsequently converted into a single GIS by Burton et al. The GIS attribute data were checked, edited and enhanced with extra data from the census by Max Satchell, Tony Wrigley and a small army of research assistants with technical support from Peter Kitson and Gill Newton. Max Satchell checked and in some cases edited the GIS polygon data using a variety of cartographic and documentary sources. Of these the most important were digital scans of the Ordnance Survey first edition 1:2500 and 1:10560 maps from the Landmark Group distributed by Edina , the series of maps of registration districts and sub-districts boundaries prepared for the Registrar General prior to the censuses of 1861, 1871 and 1891 and the description of enumeration district boundaries given in the Census Enumerators Books for the censuses from 1851, 1861 and 1871. The 1:63,360 maps and Census Enumerators Books are held in The National Archives, Kew (TNA, RG 18/3-155, 198-227, HO 107, RG 9, RG 10). The work involved changing one or more elements of information about place, parish, county, or three figure census number for 2,461 (10.8 per cent) of 22,729 lines of data in the Kain and Oliver GIS. This editing process saw the redigitisation of 644 of the 22,729 polygons, the deletion of 81 polygons, and the digitisation of 525 new polygons. The original Kain and Oliver parish and place dataset did not give details of which counties its units belonged to in 1831, though the authors did note some units had changed county under the auspices of the act of 1844. Max Satchell with help from Geoffrey Stanning and input from Peter Kitson and Tony Wrigley added the 1831 census counties as an attribute to the parish GIS primarily by systematic comparison between the censuses of 1831 and 1851 - the latter's footnotes being particularly informative concerning changes in the county boundaries. In situations where the 1831 county boundary deviated from the post-1844 alignment the polygons from the Burton et al. GIS were subdivided. At the end of this exercise all 23,177 polygons of the enhanced parish GIS could be assigned an 1831 ancient county. This attribute was then used to generate the shapefile of ancient counties.