William Louis Petersen (born February 21, 1953) is an American actor and producer, best known for playing Dr. Gilbert "Gil" Grissom on the hit CBS series CSI: Crime Scene Investigation, and as Will Graham in the film Manhunter. Petersen was born in Evanston, Illinois, the youngest of six children of June (née Hoene; 1909–2006) and Arthur Edward Petersen, Sr. (1907–2004), who worked in the furniture business. He is of Danish and German descent. He has two brothers, Arthur, Jr. and Robert, plus three sisters: Anne, Mary Kay, and Elizabeth. He graduated from Bishop Kelly High School in Boise, Idaho, in 1972. He was accepted to Idaho State University on a football scholarship. While at Idaho State, Petersen took an acting course which changed the direction of his life. He left school along with his wife, Joanne, in 1974 and followed a drama professor to the Basque country where he studied as a Shakespearean actor. Petersen was interested in Basque culture and he studied the Basque language, Euskara, and gave his daughter the Basque name Maite Nerea (meaning My Beloved); she was born in Arrasate - Mondragón 1975. Petersen returned to Idaho intent on being an actor.