The African American actor who played What Is It? was photographed in his costume by Mathew Brady in the early 1860s. Although he played the part for years, his identity is not known. Most newspaper accounts accepted the authenticity of Barnum's claims for his "monkey man" despite the obviously human image in these photographs. In 1877 William Henry Johnson, a mentally disabled African American, took over the part and performed as Barnum 's What Is It? for more than 50 years.
Source: Meserve Collection, National Portrait Gallery, Smithsonain