Patrick McCarthy

I am researching my Irish ancestors and have hit a brick wall. I'm looking for ANY information on my McCarthy ancestors who I've been told were most likely from County Cork or maybe County Limerick or Tipperary. 

My 2nd great-grandfather was Patrick McCarthy (b. 15 March 1827). Patrick was married to Mary Keenan (b. abt 1830). Both emigrated from Ireland. I don't know if they came together or separately OR if they landed in the United States or Canada. According to the 1900 U.S. Census, Mary emigrated to the U.S. in 1851 but I don't know if this was via Canada or Ireland. Unfortunately, Patrick was not on the 1900 census because he died on 19 Dec 1899 in North Prairie, Waukesha, WI. 

According to another family member, Patrick & Mary were married on 10 June 1853. (I have not found any document to verify this date.) Their first daughter, Catherine, was born in Cleveland, Cuyahoga County, Ohio on 16 March 1853. (I have not found a baptismal record to verify this date either.) However, if both dates are correct then Catherine was born before they were married. Their next 3 children, including my great-grandfather Michael Henry McCarthy, were born in Troy, Rensselear, NY between 1854-1863. Their last 2 children were born in Waukesha, WI in 1866 & 1869. 

Patrick and Mary lived in Waukesha, WI for the remainder of their lives.

Patrick's parents were William McCarthy & Johannah Cronin. I've been told they were either from County Cork or County Limerick and that Patrick had several siblings who also emigrated to the US but lost touch when they had to separate in order to find jobs. 

Mary's parents were John Keenan and Catharine Halleran. I don't know which part of Ireland they were from. 

Any information would be most appreciated. 

Thank you, 

Toni