This is a list of historic counties of England by area as at the 1831 census. Note that Monmouthshire was considered to be part of England at the time.
In England the new divisions were to be largely modelled on the existing counties with quite radical reforms put forward, even in some non-metropolitan areas. Despite reassurances from the government that nobody's loyalties were expected to change as a result of the local government reform, many changes did incur significant local opposition.
The Isle of Ely is a historic region around the city of Ely now in Cambridgeshire, England but previously a county in its own right. Changes made 1965 and 1974. The geographic counties which existed before the local government reforms of 1965 and 1974 are referred to as '"ancient counties'", historic counties or "Real Counties" - see above list.