The Mano River Union emerged from a new phase of official cooperation between Liberia and Sierra Leone. In 1973, William Tolbert and Siaka Stevens established the union as a bilateral framework linking their neighbouring states. Its creation followed Tolbert’s more active continental diplomacy and Stevens’s consolidation of power in Sierra Leone.

The union was designed to establish a customs union and additional forms of economic cooperation. It therefore addressed practical economic relations rather than proposing a political federation. The initiative was especially significant because it connected two countries whose earlier relations had involved contrasting political identities and competing claims to represent similar forces.

The union also reflected the wider regional search for institutions that could secure cooperation while preserving state sovereignty. Liberia and Sierra Leone remained distinct political communities, but the Mano River framework created an official channel for coordinating economic interests across their shared West African environment.