Kellers - information. Visiting the area.

I have relatives coming to the Castle Island, Kerry Co. area in a few weeks.  They will be atempting to do some research for John and\or Catherine Keller.  John was born abt 1828 and Catherine was born abt 1832.

Small amount of information is that they met on the boat, but supposedly, they had the same last name before then????

I have a copy of the marriage certificate from Washington DC, Jan 4th 1851 that states John Keller and Catherine Keller were married.

Their grave stones indicate that they were originally from this area.  They are buried in Cynthiana, Kentucky, US.

Any help and\or hints on where my relatives can visit to do some research, would be great.

Thanks.  Doug Kirby