Listed below are search terms for you to use when searching for resources about American Literature.
African American Literature and Culture Society
American Comparative Literature Association
American Literature Association
American Religion and Literature Society
American Theatre and Drama Society
Asian American Writers Workshop
Association for the Study of Indian Literature (ASAIL)
Association for the Study of Literature and the Environment
Circle for Asian American Literary Studies
MELUS: Society for the Study of Multi-Ethnic Literature of the United States
MLA: Modern Language Association
Modern Humanities Research Association
PEN (Poets, Playwrights, Essayists, Editors, Novelists)
Science Fiction Research Association
Society for the History of Authorship, Reading and Publishing (SHARP)
Society for the Study of American Women Writers
Society for the Study of Southern Literature
Society of Early Americanists (SEA)
Western Literature Association
Digital libraries & archives are great ways to view primary sources or full texts without having to travel anywhere. Listed below are a few digital collections of American literary greats.
Many libraries will at the very least post a collection's finding aid online. To search for these, try typing the author's name followed by "digital papers" or "collection finding aid". For example, Princeton has a large collection of F. Scott Fitzgerald's papers and writings. They are not digitized, but, you can see a list of what papers are there and discover it may be worth a trip to Princeton to see the materials in person.
All these websites are primary sources.