Duchy of Anhalt
On 27 November 1847 he inherited the Duchy of Anhalt-Köthen from his distant cousin Duke Henry. As a result of a treaty concluded with Anhalt-Bernburg in May 1853 his duchies were joined together and named Anhalt-Dessau-Köthen, because the eventual inheritance of Leopold over all the Anhalt duchies seemed inevitable. The death of another distant cousin, Duke Alexander Karl, on 19 August 1863 resulted in the ruling line of the duchy of Anhalt-Bernburg becoming extinct, thus Leopold inherited that duchy as well. On 30 August he assumed the title "duke of Anhalt."