I have information on family of Michael Rouan & wife Catherine (Sheridan) who came from Ireland to England then to Youngstown, OH, which isn't far from Mercer Co., PA. I found them in 1880: 1880 Census - Youngstown, Mahoning Co., OH - 2 Jun 1880 pg. 20 - Caughrige Lane ?(hard to read) #141-164 - ROWEN, Michel wm 57 head- Laborer b. Ire fb Iremb Ire .......Catherine wf 45 wife-kpg hs b. Ire Ire Ire .......John wm 20 son - Laborer b. Eng Ire Ire (b.1860 .......Ellen wf 14 dau - at sch b. OHIre Ire (b.1866 .......Michael wm 13 son - at sch b.OH"" (b. 1867 .......Patrick wm 12 son - at sch b.OH"" (b. 1868 .......Annie wf 9 dau - at sch b. OH""(b. 1869
There is another daughter Mary b. abt 1860 England married to Thomas Hogan living a few doors away and correspondence with desc. show a Bridget, Catherine and James belong here also.
I could not find this family in 1870 census, but they must have been there somewhere. 1900 and 1910 the mother Catherine is a widow living with daughter Annie Welsh in Youngstown.