Looking for ancestors from County Donegal

Hello!  I'm so glad I found this message board.  I'm looking for my ancestors from County Donegal.  I have four great-great grandparents who all came from Letterkenny.  They are shown in the attached image.  Surnames are:

• McCrudden (could be McCredden, McCreddan, Rodden or Rudden)
• Moss
• Crossen
• Deeney

All four emigrated to the United States around 1850.  All four were born in the 1820s and 1830s.  Both couples married in the United States and ended up in Shamrock, Wisconsin, where they are all buried in the same cemetery.  I am trying to find information on any/all of their parents, but I've been able to locate a single record that would give me this information.  Are there any descendants out there who know more information, or where I can find it?  Any help would be much appreciated.

-Maddie