Lost in Our Maps: A History of Cartographic Catastrophes - WSJ.com: But my favorite cartographic error is the Mountains of Kong, a range that supposedly stretched like a belt from the west coast of Africa through half the continent. It featured on world maps and atlases for almost the entire 19th century. The mountains were first sketched in 1798 by the highly regarded English cartographer James Rennell, a man already famous for mapping large parts of India.
The problem was, he had relied on erroneous reports from harried explorers and his own imagined distant sightings. The Mountains of Kong didn't actually exist, but like an unreliable Wikipedia entry that appears in a million college essays, the range was reproduced on maps by cartographers who should have known better. It was almost a century before an enterprising Frenchman actually traveled to the site in 1889 and found that there were hardly even any hills there. As late as 1890, the Mountains of Kong still featured in a Rand McNally map of Africa.