Natural England took over the role of designating and managing SSSIs from English Nature in October 2006 when it was formed from the amalgamation of English Nature, parts of the Countryside Agency and the Rural Development Service. Natural England, like its predecessor, uses the 1974–1996 county system and as such the same approach is followed here, rather than splitting these sites between the County Durham and North Yorkshire lists. The data in the table is taken from Natural England's website in the form of citation sheets for each SSSI.