Deaf history is an important part of Deaf culture. There are a number of websites with more information on Deaf history.
British Deaf History Society
The primary group for Deaf history in Britain. The charity has published various books and campaigns for Deaf history to be more widely recognised.
This online forum has a section on Deaf history.
RAD has extensive archives which are held at the London Metropolitan Archive. [On the RAD website go to "RAD and its Services > History and archives"]
A superb supplier of books and resources about deafness, sign language, Deaf culture and history.