Mary Reilly/Riley was born ca. 1813, likely in Ardcarne Parish in County Roscommon. Her exact birth date and parents are unknown.
On the 17th of July 1844 she married James Henderson (b. ca. 1817 in County Dublin) in Ardcarne Parish, Church of Ireland in County Roscommon. At the time of their marriage her parish was Ardcarne and his was Mohill.
Their daughter, Mary Ann Henderson, was born on the 22nd of November 1845 and baptised in Ardcarne Church of Ireland on the 11th December 1845. Their address at the time of the baptism was Errironagh (spelling variations include Errerona) in the Civil Parish of Ardcarne. The following is a picture of the baptismal font in Ardcarne Church at which Mary Ann was baptised (shown with three of Mary Ann's great-great-great grandchildren).
In 1852 Mary, her husband James, and their daughter Mary Ann were living in a shanty in Fitzroy Township in Canada West (present day Ontario), according to the 1851 Canadian Census (actually enumerated in 1852). Another child, a 3-year-old son named George (b. ca. 1849), had been born in Fitzroy Township, meaning the family likely immigrated to Canada between 1846 and 1848 and likely passed through Grosse Ile quarantine station. (Ardcarne parish, and County Roscommon as a whole, had been hit particularly hard by the Famine). Two more children, Margaret (b. ca. 1851) and Ellen (b. ca. 1857) were born in Fitzroy Township.
By 1861 the family had made their way to McKillop Township in Huron County, Canada West (Ontario) where they established a farm and lived out the remainder of their lives.
Mary Riley died in 1888 at the age of 75 years. She is buried in Maitlandbank Cemetery in Seaforth, Ontario, Canada with her husband James Henderson who died in 1905.