Roger: These are the Mary O'Brien's in 1870 Cambridge, MA. Mary Obrien found in: Census Microfilm Records: Massachusetts, 1870 Age:  19      Gender:  F      Race:  W      Birthplace:  IREL      State:  Massachusetts      County:  MIDDLESEX      Locale:  1-WD CAMBRIDGE      Series:  M593      Roll:  623      Part:  1      Page:  247A      Mary Obrien found in: Census Microfilm Records: Massachusetts, 1870 Age:  22      Gender:  F      Race:  W      Birthplace:  IREL      State:  Massachusetts      County:  MIDDLESEX      Locale:  1-WD CAMBRIDGE      Series:  M593      Roll:  623      Part:  1      Page:  303A Mary Obrien found in: Census Microfilm Records: Massachusetts, 1870 Age:  30      Gender:  F      Race:  W      Birthplace:  IREL      State:  Massachusetts      County:  MIDDLESEX      Locale:  4-WD CAMBRIDGE      Series:  M593      Roll:  624      Part:  1      Page:  644A      Lucy Whoever said "Seek and ye shall find" was not a genealogist.