Niger River

The Niger River is the principal river of western Africa, extending over 2500 miles (about 4000 km). It runs in a crescent through Guinea, Mali, Niger, Benin and Nigeria, discharging through a massive delta into the Gulf of Guinea. The Niger is the third longest river in Africa, exceeded in length by only the Nile and the Congo River (also known as the Zaire River).

The Niger takes one of the most unusual routes of any major river, a boomerang shape that baffled European geographers for two millennia. Its source is just 150 miles inland from the Atlantic Ocean, but the river runs eastward away from the sea into the the Sahara Desert, then takes a sharp right turn and heading southeast and then south to the sea.

This strange geography comes about because the Niger River is two ancient rivers joined together. Before the Sahara Desert dried up in 4000-1000 BCE, the upper Niger, from the source past the fabled trading city of Tombouctou to the bend in the current river, emptied into a now-disappeared lake. The lower Niger started in nearby hills and flowed south into the Gulf of Guinea. As the Sahara dried, the two rivers altered their courses and hooked up.

Ancient Romans thought that the river near Tombouctou was part of the Nile River, while early 17th-century European explorers thought that it flowed west and joined the Senegal River. Its true course was only firmly established in the late 19th century.