O'Regan worked as a tenant farmer during his early years in Ireland, before he moved to London in 1852.

While living there, O'Regan married an Irish refugee named Catherine Mulcahey, and anglicized his family surname to "Reagan" before emigrating to Carroll County, Illinois in 1856.

[1] John Michael, their son, became a grain elevator farmer, and married Jenny Cusick in 1878.

[2] At the time of his second son Ronald's birth in 1911, the 27-year-old Jack was working at a store in Tampico, Illinois.

He was a keen supporter of the United States' involvement in World War I and attempted to enlist.