Harper Pennington art links 

Harper Pennington: New York, 1904
Source: The Athenaeum (see "image archives" below)

Harper Pennington at the Metropolitan Museum of Art, New York City  
Beach Scene

Harper Pennington at the National Gallery of Art, Washington D.C.
Portrait of Whistler with a Paintbrush, pen and ink

Harper Pennington at the Smithsonian American Art Museum, Washington D.C.

 
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)

 

Harper Pennington at The Athenaeum  
New York, 1904

 

Maryland ArtSource

 

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