From the Wikipedia page 
Sömmerda (German: Landkreis Sömmerda) is a Kreis (district) in the north of Thuringia, Germany. Neighboring districts are (from the north clockwise) the districts Kyffhäuserkreis, the Burgenlandkreis in Saxony-Anhalt, the district Weimarer Land and the district-free city Erfurt, and the districts Gotha and Unstrut-Hainich.
The district Sömmerda was created in 1952. In 1994 the districts of Thuringia were reorganized, and the district Sömmerda was enlarged significantly by adding municipalities from the dissolved districts Artern and Erfurt-Land.