He created the largest state by area in 19th-century East Africa in present-day Urambo district in Tabora Region of Tanzania.

He owned trade caravans traveling from the Great Lakes region in western Tanzania to the coast, mostly dealing in ivory and slaves.

[1] With his newly gained power, he toppled the traditional monarchy of the kingdom of Urambo, and installed himself as ntemi (king).

[3] Mirambo was based in an area with tsetse fly infestations, which meant that transport of goods was almost completely by people rather than with the aid of animals.

Mirambo's success can be traced in part to his associations with the Watuta, a group of Ngoni people who were connected with Zwangendaba.

With ongoing wars in southern Africa as Shaka had expanded Zulu power many people had fled north, this particular group settling near Bukune.

By the time of his death, he had united most of northern Unyamwezi in an alliance under his leadership, but he never managed to conquer Tabora.