Their are four African American men whose signatures appear on US Currency. There is one woman whose signature appear on US currency during her tenure 1977-1981. As you know from the prior post Azia Taylor-Morton was the first and only Treasurer in the US. Whereas, the other men served as Registrars and not Treasurer their names also appear on US Currency.
You can click on the names below and learn more about each of the men.
Blance Kelso-Bruce was a Registrar in the US Treasury 5/21/1881 – 6/5/1885
Judson W. Lyon Registrar in the US Treasury April 7, 1898 to April 1, 1906 (Also click this link to see a picture of one of the bills with his signature on it.)