In 1866, the Scottish missionary and explorer David Livingstone returned to Africa, once again in search of the source of the Nile. Arriving in Zanzibar, Livingstone travelled westward towards Lake Tanganyika and into the Congo basin, basing himself at the village of Ujiji (now in Tanzania). Remaining in Africa for four years with no contact with the wider world, he was ill for much of the expedition and only one of his letters made it back to Zanzibar and thence to Europe, leading several people to believe that he had gone missing.

In 1869, Henry Morton Stanley was hired by the New York Herald to lead an expedition in search of Livingstone. Arriving in Zanzibar in early 1871, Stanley travelled 700 miles through Tanzania and, in November, found Livingstone at Ujiji. Stanley claimed to greet Livingstone with the now famous phrase “Dr Livingstone, I presume?” . The event was illustrated in Stanley's published account of the expedition following his return. The copy in the Royal Library has a bookmark placed at the spot. However, neither man mentioned the phrase in their journals or letters, its first appearance coming in the Herald’s publication of Stanley’s reports in July 1872. Stanley remained with Livingstone for the remainder of the latter’s expedition where they discovered no connection between Lake Tanganyika and the Nile..

Stanley would return to Africa in 1874 to lead a major expedition to explore the Congo basin, an account of which he published in 1878. Stanley’s books led to many of the late nineteenth century perceptions of Africa as ‘Darkest Africa’ or the ‘Dark Continent’, a term that he invented. He would go on to assist the Belgian king, Leopold II, in his colonisation of the Congo in the 1880s, despite often disagreeing with the king's approach.