Mali's most fertile agricultural area lies in the valley of this major west African river
... From there the Niger once 
dropped more than 1,000 feet (300 metres) in about 40 miles (60 km) into a 
valley ... its largest tributary on the right, after which it enters a region of lakes, 
creeks, and... [DOC] [TLE] History of West Africa - Wikipedia [PAR] The history of West Africa began with the first human settlements around 12,000 
BCE.