Researching mortgages may help you plug some of the holes in your deed research. Sometimes deeds were not recorded until the property actually transferred out of the family, but mortgages were always recorded at the time money was exchanged. While the mortgage looks similar to a deed, it usually contains additional information of great interest to house historians. You will generally find a more detailed description of any buildings located on the property as it was common for insurance to be a requirement of the loan.
Hopefully your local government center, library or historical society will have mortgage indexes available. If so, you can look up the property owners listed on the deeds you have already located. Look up the grantee in the mortgage index for that year. Keep in mind, however, that some people did not use mortgages as the way they financed their property purchase.
As you are looking at the deeds, a clue as to the existence of a mortgage is when $1.00 is listed as a consideration payment. This usually indicates that the property was financed through a mortgage. An additional clue is if the deed indicates a sale price significantly less than a previous sale. Unless the sale occurred during the depression or after a natural disaster, this probably indicates that the remainder of the sale price was paid by a mortgage. If you are lucky enough to come across mortgage indexes, they can help you fill in some of the gaps in your chain of title.