Excellent sites to use for your personal investigation
Library of Congress
http://www.loc.gov/library/libarch-digital.html
SFMOMA San Francisco Museum of Modern Art
http://www.si.edu/ResearchCenters/Archives-American-Art
Whitney Museum of American Art
http://whitney.org/
The Museum of Modern Art (MoMA) NY
http://www.moma.org/
TATE Museum UK
http://www.tate.org.uk/
The Metropolitan Museum of Modern ART
http://www.metmuseum.org/
http://www.metmuseum.org/toah/
Art21- For Contemporary Artists
http://www.art21.org/
V&A Museum
https://www.vam.ac.uk/
Library of Congress
http://www.loc.gov/library/libarch-digital.html
SFMOMA San Francisco Museum of Modern Art
http://www.si.edu/ResearchCenters/Archives-American-Art
Whitney Museum of American Art
http://whitney.org/
The Museum of Modern Art (MoMA) NY
http://www.moma.org/
TATE Museum UK
http://www.tate.org.uk/
The Metropolitan Museum of Modern ART
http://www.metmuseum.org/
http://www.metmuseum.org/toah/
Art21- For Contemporary Artists
http://www.art21.org/
V&A Museum
https://www.vam.ac.uk/