I'm back from North Carolina and Michigan, but now traveling throughout the northeast on a research trip.
Yesterday, I spent some time at the Library of Congress, and today I am in Philadelphia at the Historical Society of Pennsylvania. The HSP has one of the best collections of 18th-c. manuscripts in America. That's the good news. The bad news is that the society does not list their collections online. This means that you have to go to the society and physically look up the manuscripts on an ancient card catalog system.
When I finish my research at the HSP it's on to Yale's Beinecke Library and the Connecticut Historical Society in Hartford. These are two major stops for me since both Yale and the CHS hold manuscripts that I intend to use for my forthcoming evangelical reader.