The Plymouth County Sheriff’s Department, led by Sheriff Joseph D. McDonald, Jr. It is one of the oldest law enforcement agencies in the nation. The department traces its origins to the arrival of the Mayflower in 1620, when Myles Standish assumed responsibility for maintaining civil law and order as Plymouth Colony’s military leader.

The colony’s first formal law enforcement agency, the Office of Constable, was created in 1633 with the charge of maintaining peace and holding people charged with crimes. The Office of High Sheriff was established in 1692, and became an elective office in 1855. Sheriffs are elected to six-year terms.

The three primary responsibilities of the sheriff are to operate the Plymouth County Correctional Facility; assist in public safety throughout the county; and oversee delivery of legal documents needed to support the operation of the courts.

The Plymouth County Correctional Facility houses approximately 1,650 inmates, making it the largest correctional facility under one roof in New England. The jail holds a diverse male inmate population, including county, state and federal prisoners. Some have been sentenced; others are awaiting trial. PCCF also houses the state's only secure juvenile facility. Opened in 1994, PCCF's design and operation reflects contemporary corrections management practices. PCCF is accredited by the American Correctional Association and in its most compliance audit the facility received a 100% score through recent county public safety efforts.

The department also supports its K-9, Warrant Apprehension, Mounted, Motorcycle, and Honor Guard. The Communications Department coordinates all fire mutual aid in the county, serves as the communications link between paramedics and hospitals, and provides communications services at the scene of major events. The Bureau of Criminal Investigation assists local police in collecting and analyzing evidence from crime scenes, and in photographing major traffic accident scenes. All public safety support services are provided at the request of local police and fire departments.

The Civil Process Department, headquartered in Brockton, dispatches deputies to serve legal documents in civil cases. Fees paid by attorneys and plaintiffs for delivery of these documents fund the division’s operation.

Today, the Plymouth County Sheriff's Department employs more than 700 professional people, making it one of the largest employers in Plymouth County.