Actually, in most places other than Hampton Roads, the sheriff is the only law enforcement official. It just happens that the 7 cities in this area are all independent cities and don't belong to a county and that's why the police patrol the city while the sheriff's office does the jail. In the areas that have a city police department as well as county sheriff's departments, the city police stay within the boundaries of that city while the county sheriff's office has jurisdiction over the whole county including the city.