Mary Marg Helgenberger (born November 16, 1958) is an American actress. She began her career in the early 1980s and first came to attention for playing the role of Siobhan Ryan on the daytime soap opera Ryan\'s Hope from 1982 to 1986. She is best known for her roles as Catherine Willows in the CBS police procedural drama CSI: Crime Scene Investigation (2000–12, 2013) and the subsequent TV movie Immortality (2015) and as K.C. Koloski in the ABC drama China Beach (1988–91), which earned her the 1990 Emmy Award for Outstanding Supporting Actress in a Drama Series.\n', '

She is also known for roles in the TV series Under the Dome and Intelligence, and the films Species (1995), Species II (1998), Erin Brockovich (2000), and Mr. Brooks (2007).\n', '

Helgenberger was born in Fremont, Nebraska, to Mary Kay (née Bolte), a nurse, and Hugh Helgenberger, a meat inspector. She was raised in North Bend, Nebraska, where she graduated from North Bend Central High School. Helgenberger is of Irish and German descent and had a Roman Catholic upbringing. She has one older sister named Ann and a younger brother named Curt. Helgenberger played the French horn in her high school marching band. Until she went to college, Helgenberger aspired to be a nurse like her mother, but attended Kearney State College (now the University of Nebraska at Kearney) in Kearney, Nebraska, then attended Northwestern University\'s School of Speech in Evanston, Illinois, (now the School of Communication) and earned a B.S. degree in speech and drama.\n', '

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