It was formed in June 1963 from the Benin and Delta provinces of the Western Region, and its capital was Benin City. It was designated as a province in 1966. In 1967 when the other provinces were split up into several states, it remained territorially intact and become a state.
During the Nigerian Civil War, the Biafran forces invaded the new Mid-Western state, en route to Lagos, in an attempt to force a quick end to the war. While under Biafran occupation, the state was declared as the "Republic of Benin" as Nigerian forces were about to retake the region. The republic collapsed a day after the declaration when Nigerian troops overtook Benin City