The first European to report the existence of the Congo was the Portuguese navigator Diogo Cão in 1482 and within thirty years the Portuguese appetite for slaves was causing political tensions between both kingdoms. History then follows the usual dismal path of colonial exploitation, the only significant difference being that the upper Congo could not be reached from the coast because the huge river descends from the central African plateau to the sea in numerous cataracts and precipitous cliffs. The Congo basin therefore remained unexplored by Europeans until 1877 when Henry Morton Stanley descended the river from the headwaters to the sea.
Henry Morton Stanley (q.v.) had distinguished himself as a journalist in reporting …
Clark, Robert. "Henry Morton Stanley travels from the Congo to the Atlantic". The Literary Encyclopedia. First published 01 April 2002
[https://www.litencyc.com/php/stopics.php?rec=true&UID=16299, accessed 22 March 2019.]