Mary Catherine McCormack is an American actress. She has had leading roles as Justine Appleton in the series Murder One , as Deputy National Security Adviser Kate Harper in The West Wing and as Mary Shannon in In Plain Sight .
McCormack was born in Plainfield, New Jersey. She is the daughter of clinical therapist Norah and car dealership and ice cream parlor owner William McCormack. Her parents divorced in 1990. Her sister Bridget is a justice of the Michigan Supreme Court, and a former professor of law at the University of Michigan Law School, and her brother William is an actor who has appeared in a recurring role as FBI agent Robert OConnor on In Plain Sight.
Source: Wikipedia