Before 1235 Herzogtum Sachsen,
1235 - 1437 Herzogtum Braunschweig-Lüneburg,
1437 - 1692 Fürstentum Calenberg,
1692 - 1806 Kurfürstentum Braunschweig-Lüneburg (official name, Kurfürstentum Hannover was a colloquial name among others),
All constituent states of Heiliges Römisches Reich.
There were very frequent splits and accessions of other territories, so that a precise location is needed to get the territory right.