What is the best place to write to find out about William and Susannah Ward? Which entity is most like to know about them? Library, Historical Society or other?

I believe my ancestor was their son William W. Ward. He appears to be the one living near Susannah. Any other William Ward found in the NY Census in 1810 does not have the right # and age children. I think that my William W. Ward was in Cayuga County in 1820. I have not been able to trace any land records in NY in either county. William W. was in Erie County, PA by 1830. He did own land there. Marlene