The East African Development Bank (EADB) was originally established through the Treaty for East African Co-operation, signed in 1967. This treaty created the institutional framework for economic cooperation among Kenya, Tanzania, and Uganda, including the establishment of the development bank to finance regional projects. Option A is correct - the 1967 Treaty for East African Co-operation established the bank. Options B (1965) and C (1968) have incorrect years and treaty names, while Option D is incorrect as option A is accurate.