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 (See Sierra Leone Civil War, First Liberian Civil War, Second Liberian Civil War).
Liberia and Sierra Leone founded the Mano River Union in 1973, Guinea joined in 1980. It was reactivated in 2004 as a customs and economic union; Côte d'Ivoire joined in 2008.