McGarrs in the East of Ireland

Hi Everyone,
I am trying to research my family name. I don't have a lot of information and am hoping someone here might have some information. My Grandfather (James Mcgarr) came to the USA in 1874 and settled in New Haven Connecticut before moving to the pacific northwest. I'm trying to find any relatives in the east of Ireland in particular a family that has six daughters and four sons. Is there an online census where I may be able to find them? I don't have any first names.
Alyssa
Olympia, WA