American Museum of Natural History scientists Herbert Lang and James Chapin left New York Harbor bound for the African Congo on May 8, 1909. The Lang-Chapin Congo Expedition was originally funded for two years. In the end it spanned six years, from 1909-15. The mission, in the minds of the explorers and the museum's administrators, was to capture as broad a picture of the Congo's biota and cultures as possible. The Congo expedition focused on a pair of animals so rare and exotic that they were almost mythical: the okapi and the square-mouthed rhinoceros,also known as the white rhinoceros.

As their experience in Africa deepened, Lang and Chapin became increasingly interested in the African people they were living and working with. Lang, although not formally trained in Anthropology, wrote the field catalouge for the ethnographic collection and collected material ranging from grain samples to head measurements, household items, and finally, at the end of his stay, works of commissioned art. Lang's commitment to empirical observation led him to collect masses of information about material culture and the people who produced it. Although the Lang-Chapin ethnographic collections include objects from regions all along the expedition's route, the largest and most important part of their collection is from the Mangbetu.

With the outbreak of World War One, Lang and Chapin made their way back to New York. They had collected the most complete record of the plants, animals, and cultures of the Congo Basin up to that time, including 5,800 mammals, 6,400 birds, 4,800 reptiles and amphibians, 6,000 fish, over 100,000 invertebrates, and 3,800 anthropological objects. In addition, they had 9,890 photographic negatives, more than 300 watercolor paintings, and many volumes of field notes. At least fifteen volumes of scientific findings were later published based on the expedition's work, many of which continue to stand as both seminal and definitive works in their fields.