Potsdam-Mittelmark is the most populous district in Brandenburg. It was established upon the enactment of the Law on the Reorganization of the Districts and Independent Cities in the State of Brandenburg (Gesetz zur Neugliederung der Landkreise und kreisfreien Städte im Land Brandenburg festgelegt; aka, Kreisreform Brandenburg), which was announced on December 24, 1992, and put into effect on December 6, 1993. The Law restructured and reduced the number of Brandenburg districts from 38 to 14. The new Potsdam-Mittelmark District was formed from the districts of Brandenburg, Belzig and Potsdam, and the administrative unit of Treuenbrietzen.
