Born 1840, Moscow, Russia
Died 1892

By the last decades of the nineteenth century, much of the interior of the continent of Africa had been explored and mapped. Still, there were some areas that had not yet been investigated or where geographical questions remained. One such region was located between the upper reaches of the Nile and the Congo, the continent’s two great rivers. Mapping the Congo River—which extends through much of central Africa—was especially difficult because of its numerous large and small tributaries. The Congo and its branches form a system of navigable waterways some 9,000 miles long.

One explorer who helped add some geographical answers to the puzzle of Africa’s complex waterways was Wilhelm Junker. He was born in Moscow, Russia, in 1840, to German parents. At the age of twenty-nine he sailed to Iceland, beginning a life of travel...