Following Spain’s 1898 defeat in the Spanish-American War, it sold its remaining Pacific possessions, including the Mariana Islands, to Germany.
On 18 June 1899, the German government declared Marianen to be a German colony, with its headquarters at Garapan on the island of Saipan. A post office was opened there on 18 November 1899.
With the outbreak of World War I, steamship traffic to and from Saipan was significantly disrupted. The last known mail departure from Saipan was in early September 1914. Saipan was occupied by Japanese forces on 14 October 1914, forcing the closure of the German post office.