Literature is a body of literary materials that can be anything from creative to technical or scientific works of a language or culture.
All cultures and languages have literatures one way or another, in which they pass on their stories, poems, plays and other works that reflect their experience, tradition, and values of a culture of people. Language and culture are interwoven that they do not exist without each other.
Literature has two forms: oral (whether spoken or signed) and written.
ASL like other languages (signed or spoken) has literature of its own that has been passed on from a generation to another by Amelsan people (culturally Deaf/native signers).
H-Dirksen L. Bauman, et al. Signing the Body Poetic: Essays on American Sign Language Literature.
H-Dirksen L. Bauman. "Redesigning Literature: Poetics of American Sign Language Poetry". http://www.ubu.com/ethno/discourses/bauman_asl.html
Supalla, Sam; Bahan, Ben. Bird of a Different Feather and For a Decent Living. (DVD)
Also see Literacy in sign language.