West Africa
People have probably been living in West Africa for thousands of years.
There are several good-sized rivers - the Niger, the Senegal, and the
Volta - which make it easier to travel because you can use boats.

Niger river
There are fish in the rivers which are good to eat. These rivers also, when they flood, spread good silt all over the land, which makes the land good for growing plants. The rivers do also breed the mosquitoes that carry yellow fever and malaria, but people living in West Africa gradually developed immunities to these diseases.
West African people in Nigeria were smelting iron by around 400-200 BC. We don't know whether they invented this process themselves, or learned about it from North Africans.
Around this same time, some of these people, perhaps from a little further east in modern Cameroon, were beginning to leave West Africa and travel east, across the African grasslands south of the Sahara Desert, and south-east through the rain forests. They probably didn't all leave at once, but in small groups, now and then, moving gradually through eastern and then southern Africa. These travellers are generally called the Bantu, which means "people" in their languages. Their iron weapons may have helped them to force their way into the communities they met.
By 400 AD these Bantu people had reached South Africa, where they began to marry some of the Khoikhoi and the San people. Some people in South Africa began farming or keeping sheep or cattle around this time; others, who wanted to remain hunters and gatherers, were forced off the best agricultural land and into the deserts.
But many Bantu people also stayed in West Africa. For instance, there were certainly people living at Djenne-Djeno, in modern Mali, far up the Niger river in West Africa, around 250 BC. By 300 AD, the men and women of Djenne-Djeno were trading along the Niger river with other West African communities to get iron and good stone to make grindstones. They buried dead people in tall pots that stood in between their houses.
By 500 AD, there were about 20,000 people living in Djenne-Djeno in West Africa, more than in most European towns of that time. There were also smaller towns around the main town. They kept on working iron, and by now were also working copper, which came more than 1000 kilometers (about 600 miles) to get to Djenne-Djeno. They sold their pottery up and down the Niger river as far as 750 kilometers (450 miles) away.
