Scattered holdings of Furman material relating to his interests in blacks and Indians can also be found in the Smithsonian Institution's National Anthropological Archives. They appear in the papers of ethnologists he corresponded with, notably those of Albert S. Gatschet. These strange people fascinated him for many years and the new material includes both letters and articles he produced in his attempts to track down their history. The manuscripts record Furman's investigations of common Redbone family names like Goins, Chavis, and Oxendine, and his correspondence with authorities on similar and possibly related ethnic groups. One of Furman's clippings recounted James Mooney's theory of possible Portuguese ancestry for the Pamunkeys, Croatans, Melungeons, and other groups.
Some items are of outstanding historical value.
On 27 May 1897, The State published Furman's biographical sketch of Redbone patriarch James Edward Smiling, a Sumter County legislator in the radical General Assembly from 1868 to 1870. Information on Reconstruction figures like Smiling is often difficult to find. On 17 May 1893, Bennettsville historian J.A.W. Thomas sent Furman four pages of detailed information on mixed breeds in Marlboro County. Some families among them had rendered distinguished service during the Revolution and won the respect of the white people. Often, however, Furman's search for information on mixed breed families yielded evidence of criminal activity.