George Eastman was the founder of the Kodak Company. His museum in Rochester, NY, holds over 400,000 photographic objects, many of which are available digitally here.
The Library of Congress is your library. The prints and photographs online catalog allows you to search numerous collections of images held by Library of Congress.
The New York Public Library Digital Collections is comprised of over 1 million individuated images. In addition to photographs, it also includes prints, maps, and more.