The Atlantic Monthly Archive
http://ebooks.library.cornell.edu/a/atla/index.html
This index allows you to browse digital facsimiles of issues from The Atlantic Monthly; by selecting issues from 1876 and 1877, you can find images of the serialized text of The American as it first appeared to its readers.
Transcriptions of Early Letters to Henry James
http://www.dearhenryjames.org/
This website provides transcriptions of letters to Henry James from the period shortly before the writing of The American, as well as biographical and bibliographical information.
19th-Century Image of the Salon Carre, Louvre Museum
http://www.wga.hu/html_m/c/castiglj/
This site provides an image of an 1861 painting by Giuseppe Castiglione, showing the Salon Carre (featured in the first scene of the novel) as it would have looked just a few years before the action of the novel.
http://www.oxfordbibliographies.com/view/document/obo-9780199799558/obo-9780199799558-0036.xml
This site provides an excellent and detailed listing of scholarly references for learning more about Henry James and his writings.
