Looking for information on two G-Grandfathers- Cannon & McCafferty

Hello;

I am seeking anything on two of my great grandfathers, who supposedly came to the States from Donegal.  Neither knew each other, and were of different generations.  The only data I have has been gleemed from census research, and even that is sometimes contradictory. Both were illiterate so left no written record and almost as much oral.  I cannot even definitely nail down their birth years let alone birthdays.  Both were RC.

Manus Cannon was born probably in 1842, but possibly as late as 1849.  Extrapolating back from the age he used in each census that is the range I am working with.  His death certificate, filled out by his son, gives his father's name as Cornelius Cannon.  This is plausible as he named his first son, who died in infancy, Cornelius.  Manus's mother's name is unknown.  On one census he gave his year of immigration as 1865.  He married Bridgit Thompson in 1869, but they probably met here and I have zero information on her other than that she too came from Ireland.

Owen McCafferty was probably born in 1868.  His death certificate lists his father's name as Martin McCafferty and his mother's as Mary Regan.  Answers to the census show he immigrated between 1875 and 1885.  He married Catherine Gallagher in 1890, but again they probably met here.  She also came from Ireland.

I have no information as to any relatives that may have come to America with them, ships that they may have sailed on, or ports they may have used.  It seems we are a pretty closed mouth set of families.

Any possible help would be greatly appreciated.  My email is cannon23135@hotmail.com as I seem to be having some trouble with my user name and password on this site.  I hope that can be shortly sorted out.

James Cannon