You might not expect that a high school would be the site of one of America's finest art galleries, but the Addison Gallery of American Art, located at Phillips Academy, boasts a collection of nearly 17,000 pieces of painting, sculpture, photography and other media representing numerous American masters such as Winslow Homer, John Singer Sargent, James McNeill Whistler. Georgia O'Keeffe, and Jackson Pollock. Only a small number of these pieces are exhibited at any given time, but the remainder are made available through the Museum Learning Center. Amazingly, admission to all exhibits and events is free.
If you go:
The gallery is closed on Mondays, major holidays and Christmas Eve, and during the entire month of August.
Links:

180 Main Street
Andover, Massachusetts 01810 USA
addison@andover.edu
Phone Numbers:
Addison Gallery
+1 (978) 749-4015
+1 (978) 749-4015