Touring Ohio: The Heart of America has some great information on different areas of Ohio that were considered stops for slaves escaping on the Underground Railroad.
The Ohio Genealogical Society has great information for more than just the Delaware County residents; there is information in the catalog from all Ohio counties.
Numerous of online resources on different aspects of Ohio History. Locate print resources in the Ohio Archives. Can email reference librarians, but there may be a research/copy fee.
This Facebook Page is dedicated to the Lucy Depp Park and gives access to pictures and a lot of good information directly from those who currently reside in the area.