It lasted from the 1500s till 1945/1949 after/during the german occupation of east and west germany.
But it still exists today.
It used to be called mitteldeutchland by the germans or middle/central germany
By the english, and a mix of the regions; hessen and thuringia but broke apart.
But has been renamed after the border agreement to be called thuringia.
Thuringia is prussia.