The Library of Congress is a treasure trove of historical information. The huge American Memory site is housed here, and you will see links to many other digital collections that are available online. Look for the link marked "Digital Collections" at the top of the page and EXPLORE!
Andy Warhol (1928-1987) is perhaps best known for his contribution to the development of the pop art movement. His depictions of Marilyn Monroe, Muhammad Ali, and Elvis Presley are now part of American culture, as is his silkscreens of Campbell soup cans, such as the one below from 1968.
(Courtesy of ARTstor Database)