Google's new free patent search engine is a great way of researching guitar history. If you type "McCarty guitar" into the search box you can view the original 1955 patent documents for the Les Paul Guitar. You can also access the 1957 patents for the Gibson Explorer, Flying V and the rare Moderne model.

Leo Fender's numerous patents are available if you search using his full name "Clarence L Fender".

Link: Original Les Paul patent document

Link: Original Fender Telecaster patent document