The Ost-Afrikanische Hauptlinie, or East African Main Line, began in 1890, initially running from Hamburg to Zanzibar.  The eastern terminus was moved to Dar-es-Salaam in 1891, and Tanga in 1893.

In 1890,  the Deutsch-Ost-Afrika Linie (DOAL) was founded to provide service to Deutsch-Ostafrika along the Hauptlinie.  There was significant overlap in its organization and operations with the Woermann line providing service to West Africa, resulting in Woermann ships also servicing the route.

In 1901, an additional service that terminated in Portuguese East Africa instead of Deutsch-Ostafrika began, the Ostafrika-Linie.  This service used new cancellers to distinguish it from the Hauptlinie service.

Operations on the line functionally ceased with the outbreak of World War I in 1914.  In addition to it being impossible to maintain service through hostile waters, the DOAL’s contract with the German government expired during the war and wasn’t extended.  The DOAL and Woermann Linie assets were sold to a consortium led by HAPAG and Norddeutscher Lloyd, and all their ships were lost during the war or surrendered to the Allies under the terms of the Versailles Treaty.