It is always important to be aware of the organizations involved in preserving graveyard information. To quote their Website:
The Association for Gravestone Studies (AGS) was founded in 1977 for the purpose of furthering the study and preservation of gravestones. AGS is an international organization with an interest in gravemarkers of all periods and styles. Through its publications, conferences, workshops and exhibits, AGS promotes the study of gravestones from historical and artistic perspectives, expands public awareness of the significance of historic gravemarkers, and encourages individuals and groups to record and preserve gravestones. At every opportunity, AGS cooperates with groups that have similar interests.
The AGS Archives is a collection of about 1000 books and many papers written on various aspects of gravestone studies. We are always looking for more books and information to add to this collection, with a goal of eventually making it the best repository of materials on gravestone studies that there is.The Website also has some links to similar organizations in the various states.