O'Halloran - Castle Island, Co. Kerry > Oakland, Alameda Co., CA

I'm looking for info on Maurice O'Halloran (17 Nov 1821 - 2 Mar 1888).The family were from Castle Island, Co. Kerry, IRE and (somehow) ended up in Oakland, Alameda Co., CA.Maurice had brothers, James and Luke (who died in the Donner Party).

Any information will be appreciated.