My dissertation explores the relationship between anticolonialism and regionalism in West Africa by examining the popular 1910s–50s movement to unite the four British West African colonies — Sierra Leone, the Gold Coast, Gambia and Nigeria — into a single dominion under the British crown. I ask: why did this movement seek unity, and to remain within the Empire? How did the desire for regional unity among West Africa's elite — who founded the National Congress of British West Africa, the party leading this movement— influence the institutions that the elite then created in their respective colonies, such as banks, credit unions, schools, and local customary laws? Through archival research in the four African countries and in the UK, I analyze the political imaginary of the unity movement in the context of their colonies' land struggles against the British government. I hypothesize that it is no coincidence that the movement's leaders were also those most involved in fighting land confiscation by the British government, or in detailing, via customary law, important precolonial conceptions toward land. In West African epistemologies, land was not only an important form of resource or property; it was also intimately tied to local gods, ancestors, and rituals involving birth, death, adolescence and marriage. Land bound and defined communities, as well as formed a crucial interface between a society's past and present. My dissertation thus investigates regionalism as a uniquely material imaginary, not so much based on an 'imagined community', per Benedict Anderson's thesis, as a specifically 'grounded' one, which joined together 'people on land'. I argue that regionalism, in the context of Empire, was a way of spatializing community so as to integrate precolonial pasts and imperial futures.