Joseph J. Walsh Maynooth

I am searching for information on my GG Grandfather, Joseph J. Walsh.  He was born in Ireland Approximately 1828.  United States census records list his occupation sometimes as Stone Cutter and other times as a Flagger/Paver.  City Directories list him alternately in the same way.  The 1900 US census record states he emigrated in 1850.  He was a United States Civil War Navy veteran.  In his Civil War pension file his widow states that he was from Maynooth, County Dublin.  His widow was also born in Ireland and I am confused why she states that Maynooth is County Dublin and not County Kildare.  I will be posting this same message on the Dublin Booterstown Parish message board as well.  She was his third wife and they met while in the US.  He died in Passaic, New Jersey on March 29, 1902.  His death certificate lists his age as 73.  The death certificate states that he was born in Ireland as was his mother and father.  It also states his father’s name was John and his mother’s was Ann.  I have been unable to find any information closely matching this information for Maynooth.  I was able to find a baptism record on www.rootsireland.ie for a Joseph Walsh born 24 March, 1828.  The parents are listed as John Walsh and Catherine Maddock and the sponsors are Laurence O’Neal and Ann Maddock.  The Parish is listed as Booterstown Blackrock & Dundrl.  Maybe someone in the States confused his godmother and mother’s names.  Thank you in advance for any help you can give.