Joseph H. Davis art links 

Joseph H. Davis at the Metropolitan Museum of Art, New York City  
Mr. and Mrs. Daniel Otis and Child, 1834 (Zoom)

Museum of Fine Arts, Boston  
Watercolor collection online

Joseph H. Davis at the National Gallery of Art, Washington D.C.
John and Abigail Montgomery, 1836

Currier Gallery of Art, New Hampshire
2 works online

Terra Foundation for American Art, Chicago
3 works online

 
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)

 

Joseph H. Davis in the Art Renewal Center

Bildindex der Kunst und Architektur (in German)  
(a welcome screen is displayed for a couple of seconds before the search results appear)

 

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