William Valentine was born in Gettysburg, Pennsylvania. He is a graduate of Delone Catholic High School in McSherrystown, Pennsylvania (1989), and holds an A.A. in Criminal Justice from Frederick Community College (1991). He graduated from the Frederick Police Department Training Academy in 1995. His career includes service as a police officer in Thurmont, Maryland (1994–1998, 2003–2005), as a Deputy Sheriff in Garrett County, Maryland (1998–2003), as a police officer in Westminster, Maryland (2005–2019), and as an investigator for the Frederick County State's Attorney's Office (2019–2022). He was elected to the Maryland House of Delegates in November 2022 and has been a member since January 11, 2023.
