Original: The district was founded in 1920 (under the name Arnstadt); it was divided in 1952 into the districts of Arnstadt and Ilmenau, but reunited in 1994.
Simplified: The district was founded in 1920 (under the name Arnstadt); it was divided in 1952 into the districts of Arnstadt and Ilmenau, but joined together again in 1994.