The mid-nineteenth century is well-known as a period of major political change in equatorial eastern Africa. New states emerged in Ukimbu and Unyamwezi in present-day west-central Tanzania, and some already-established states, such as Buganda in present-day Uganda, consolidated and expanded. These developments are usually associated with processes of indigenous innovation in the context of the wider region’s rapid integration with the growing capitalist economy via the global ivory trade. This presentation, by contrast, incorporates recent and ongoing climatological research to add an environmental perspective to this history. While rejecting environmental determinism, it shows how some of the most prominent states in the region took advantage of a protracted period of abundant rainfall in c.1840-1875 to enhance production and administrative capacity. They did so by exploiting the natural world in new ways, such as through modified agricultural practices, introduction of cattle, and establishment of larger settlements. These changes and enviro-climatic contexts, the presentation argues, were fundamental to how the region’s mid-nineteenth-century states grew and consolidated. Further, in making this argument, the presentation draws parallels with phenomena occurring in the wider nineteenth-century Indian Ocean World, where increased environmental exploitation has regularly been considered as fundamental to political and economic life.