The Mano River is a river in West Africa. It originates in the Guinea Highlands in Liberia and forms part of the Liberia-Sierra Leone border. The districts through which the river flows include the Parrot's Beak area of Guinea, Liberia's Lofa County and the Kono and Kailahun District of Sierra Leone. Diamond mining is a major industry in these areas. Control of …The Mano River is a river in West Africa. It originates in the Guinea Highlands in Liberia and forms part of the Liberia-Sierra Leone border. The districts through which the river flows include the Parrot's Beak area of Guinea, Liberia's Lofa County and the Kono and Kailahun District of Sierra Leone. Diamond mining is a major industry in these areas. Control of the area's wealth and the instability of the national governments of all three countries led to a series of violent conflicts involving these districts in the 1990s.