After the Fourth Coalition's defeat at Jena and Auerstedt, Napoleon attached the Lordship of Blankenhain to the Principality of Erfurt, directly subordinate to himself as an "imperial state domain" (French: domaine réservé à l'empereur), separate from the Confederation of the Rhine (nominally a French protectorate set up to replace the now-defunct Holy Roman Empire), which the surrounding Thuringian states had joined.

[3] After the Congress of Vienna, Erfurt was restored to Prussia on 21 June 1815, becoming the capital of one of the three districts (Regierungsbezirke) of the new Province of Saxony, but some southern and eastern parts of Erfurter lands joined Blankenhain in being transferred to the newly promoted Grand Duchy of Saxe-Weimar-Eisenach the following September.

After being controlled briefly by the United States, from July 1945, the state of Thuringia came under the Soviet occupation zone, and was expanded to include parts of Prussian Saxony, including Erfurt, which became the new capital of Thuringia.

The State of Thuringia was restored with slightly altered borders during German reunification in 1990.

During the UEFA Euro 2024 tournament, the England national football team were based in Blankenhain.