The Middlesex Sheriff's Office is a law enforcement agency which serves the 54 cities and towns of Middlesex County, Massachusetts. The agency's primary responsibility is oversight of the Middlesex Jail & House of Correction in Billerica, Massachusetts. In addition, the MSO operates the Office of Civil Process, a community counseling center and community service programs. Established in 1692, the MSO is one of the oldest law enforcement agencies in the United States.