Dear Anne
In going back you will be dependent on the detail from that marriage cert you referred to initially. Using the names of the parents you can search the sites I mentioned for their marriage cert and the baptism of their children. That will probably be a far as you can get using online records. If you are ever in Dublin you can use the townland information to search the Cancelled Books in the Valuation Office. These give an indication who held a certain plot of land from the time of Griffith?s Valuation (1847-1864) to the 1980s/1990s. Even though you would be moving into the present with this latter source, sometimes it yields some interesting information.
Records for the Roman Catholic Parish of Rathdrum begin in 1795 for baptisms and 1810 for marriages. In nearby Avoca parish, the baptism and marriage records begin in 1778. Both of these RC parishes are in the Civil Parish of Rathdrum. As civil registration does not begin until 1864 there will be no state records available for the family until after that time. So, we are dependent on parish records.
It may be the case though that Eliza and Robert were born in a parish and at a time that predates the parish records. As you probably know, the marriage would have taken place in the home parish of the bride (as is still mostly the case today). They may have moved to Rathdrum after this.
Hope this helps
Clare
Genealogy Support