Ancestry's online magazine, The Weekly Discovery, recently publicized an interesting census that has just become available. It is the U.S. Special Census on Deaf Family Marriages and Hearing Relatives, 1888-1895. Here is the link: http://tinyurl.com/yd8gm9b to an explanation of the documents.
The Discovery offers this background: "The records in this collection were created by the Volta Bureau in Washington, D.C., to explore whether marriages where one or both parties were deaf impacted the chances that they would have children who were deaf. Questionnaires were sent to deaf couples and family members of deaf individuals that asked for information on three generations of the family—the couple’s parents and siblings, the married couple, and their children."