<Li> Full service - provide the full spectrum of police services to the entire county, irrespective of local communities, and may provide contractual security police services to special districts within the county . </Li> <Li> Limited service - provide services to unincorporated areas of the county (and may provide services to some incorporated areas by contract), and usually provide contractual security police services to special districts within the county . </Li> <Li> Restricted service - provide security police to county owned and operated facilities and parks . Some may also perform some road patrol duties on county built and maintained roads, and provide support to municipal police departments in the county . Some northeastern states maintain county detectives in their county attorneys' offices . </Li> <P> For example, the Commonwealth of Virginia does not have overlapping County and City jurisdictions, whereas in the other 49 states most municipalities fall within (and share jurisdiction and many other governmental responsibilities with) a County . In Virginia, governmental power flows down from the State (or in Virginia's case, Commonwealth) directly to either a County or an Independent City . Thus, policing in Virginia is more streamlined: the County Sheriff's Office / Department or County Police Department does not overlap with an Independent City Police Department . Unincorporated Townships remain part of their parent County, but may have Town Police Departments to augment their County law enforcement . Town Police Departments are often small, and may deploy a combination of paid and nonpaid, full and part - time law enforcement officers, including auxiliary officers who typically serve as part - time, unpaid volunteers . If present, Independent City Sheriff's Offices usually follow the Restrictive model shown below for Sheriff's Departments, with limited law enforcement authority including warrant service, jail bailiff, etc . Mutual assistance compacts may exist where neighboring law enforcement agencies will assist each other, however, in addition to State (Commonwealth) law enforcement resources . </P>

History of the police force in the united states