Here are some useful websites and databases for finding Primary Sources on disability.
Disability in the Modern World (Duke NetID needed to access) - This database contains a range of primary sources, including archival documents, photographs, issues of influential disability rights publication The Disability Rag, and episodes of the disability-focused TV show No Limits.
Disability History Museum Library - Digital library of textual and visual sources in disability history in the United States from the 19th, 20th, and 21st centuries.
National Archives - Americans with Disabilities Act - Contains documents from the National Archives pertaining to American citizens with disabilities. Includes documents relating to disability rights in the United States and links to Presidential Library websites on disability.