Mary Catherine McCormack (born February 8, 1969) is an American actress. She has had leading roles as Justine Appleton in the series Murder One (1995–97), as Deputy National Security Adviser Kate Harper in The West Wing (2004–06), as Deputy U.S. Marshal Mary Shannon in In Plain Sight (2008–12), and as Peggy in the comedy series The Kids Are Alright (2018–19). Her film roles include Private Parts (1997), Deep Impact (1998), True Crime (1999), Mystery, Alaska (1999), K-PAX (2001), Dickie Roberts: Former Child Star (2003) and 1408 (2007). Early life 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 was the Chief Justice of the Michigan Supreme Court and a former professor of law at the University of Michigan Law School. Her brother William is an actor, writer and producer who has appeared in a recurring role as FBI agent Robert O'Connor on In Plain Sight. In 1987, McCormack graduated from the Wardlaw-Hartridge School in Edison, New Jersey. In 1991, she received her BA in comparative arts, specifically painting and creative writing, from Trinity College in Hartford, Connecticut. Career McCormack began her acting career at age 12, performing in Gian Carlo Menotti's Christmas opera Amahl and the Night Visitors. She continued her stage work in musicals and finished an acting program at the William Esper Studio. She has worked in New York theater productions, including The Atlantic Theater Company, Alice's 4th Floor, and Naked Angels, where she appeared in Jon Robin Baitz's A Fair Country. McCormack portrayed Justine Appleton on Murder One (1995–1997) and also starred in the HBO series K Street, which aired for only ten episodes. She starred in Howard Stern's movie Private Parts in 1997. In 2004, McCormack joined the cast of The West Wing as Deputy National Security Advisor and ex-CIA officer Kate Harper. Her character soon became a recurring role and remained throughout the last three seasons until the series finale. McCormack starred in the USA Network series In Plain Sight. She portrayed Mary Shannon, a deputy United States marshal attached to the Albuquerque, New Mexico, office of the Federal Witness Security Program (WITSEC), more commonly known as the Federal Witness Protection Program. On July 28, 2010, the show was renewed for its fourth and fifth seasons, to run in 2011 and