Re: Francis Wagner - PA - b.1817 - d.1877
Here are a few ideas some of which you probably have already tried.
The Marx Room at the Easton Area Public Library has an excellent selection of Northampton County records. I'm guessing you've already gone through a number of church records looking for Francis in death or baptismal records.
The library has a number of newspapers on microfilm. The English language newspapers generally didn't have much on a person when they died. More often than not the most you can find is a simple death notice. The German language newspapers also had death notices but they also sometimes had obituaries (although 1877 may have been a little early for the obits). I suggest checking to see anyway. If you don't read German that may be a problem and nearly all the printing is in German Gothic type.
Records at the Northampton County Courthouse may have something on Francis at the Recorder of Deeds and Register of Wills Offices. His children may have had guardians appointed which would be in the Orphans Court records.