National Archive
https://www.archives.gov
The Met
https://www.metmuseum.org
National Gallery of Art
https://www.nga.gov/
Google Arts and Culture
https://www.google.com/culturalinstitute/beta/
Library of Congress
https://www.loc.gov/
Presidential Libraries
The J. Paul Getty
http://www.getty.edu/museum/
The Broad
www.broad.org