Thomas Wilcocks Sully art links 

Thomas Wilcocks Sully at the Metropolitan Museum of Art, New York City  
George Washington, 1840

Thomas Wilcocks Sully at the National Gallery of Art, Washington D.C.
Major Thomas Biddle, 1832

 
National Art Databases and Museum Inventories:

Smithsonian Institution Art Inventories
List of works nationwide from two sources: the Inventory of American Paintings Executed before 1914 and the Inventory of American Sculpture (only a few percent of listings have an accompanying image)

 

Union List of Artist Names (Getty Museum)  
Reference sheet with basic information about the artist and pointers to other references.