"The long stretches of the waterway ran on, deserted"
The Roi des Belges upon the Congo River (1888)
Public DomainThe Roi des Belges upon the Congo River (1888) - Credit: Alexandre Delcommune

The Congo River was not quite as isolated as the novel suggests, since by 1890 some eleven steamers were operating on a stretch of water roughly equivalent in length to the Mississippi River. However, Zdzisław Najder’s description does suggest something of the isolation Conrad may have felt:

About two hundred miles above Kinshasa the Congo becomes a huge elongated lake, interspersed with islands and shoals, with the other bank often invisible … In parts the Congo measures a few miles in width; in others it spreads over ten … several missions hundreds of miles apart … no more than six villages over a distance of more than five hundred miles.

(Joseph Conrad: A Chronicle, 1983)