Marzahn became part of Greater Berlin in 1920, as a part of the Lichtenberg district. In 1979, the large housing estate of Marzahn was separated from Lichtenberg to become an East Berlin borough in its own right and in 1986 the new Hellersdorf district (including Kaulsdorf and Mahlsdorf) was split from it. Berlin's 2001 administrative reform led to the former boroughs of Marzahn and Hellersdorf fusing into a single new borough.