By the late Middle Ages the county was being used as the basis of a number of functions.
Administration of justice and law enforcement
The Assize Courts used counties, or their major divisions, as a basis for their organisation. Justices of the peace originating in Norman times as Knights of the Peace, were appointed in each county. At the head of the legal hierarchy were the High Sheriff and the Custos rotulorum (keeper of the rolls) for each county.
The justices had responsibility for maintaining county gaols and houses of correction. During the 19th century penal reformers campaigned against the often primitive conditions in gaols, and under the Prison Act 1877 they came under Home Office control.
Until the 19th century law enforcement was mostly carried out at the parish level. With an increasingly mobile population, however, the system became outdated. Following the successful establishment of the Metropolitan Police in London, the County Police Act 1839 empowered justices of the peace to form county constabularies outside boroughs. The formation of county police forces was made compulsory by the County and Borough Police Act 1856.
In the 1540s the office of Lord Lieutenant was instituted. The lieutenants had a military role, previously exercised by the sheriffs, and were made responsible for raising and organising the militia in each county. The lieutenancies were subsequently given responsibility for the Volunteer Force. In 1871 the lieutenants lost their positions as heads of the militia, and their office became largely ceremonial. The Cardwell and Childers Reforms of the British Army linked the recruiting areas of infantry regiments to the counties.
Each English county sent two Knights of the Shire to the House of Commons (in addition to the burgesses sent by boroughs). Yorkshire gained two members in 1821 when Grampound was disenfranchised. The Great Reform Act of 1832 reapportioned members throughout the counties, many of which were also split into parliamentary divisions. Constituencies based on the ancient county boundaries remained in use until 1918.
From the 16th century onwards the county was increasingly used as a unit of local government as the justices of the peace took on various administrative functions known as "county business". This was transacted at the quarter sessions, summoned four times a year by the lord lieutenant. By the 19th century the county magistrates were exercising powers over the licensing of alehouses, the construction of bridges, prisons and asylums, the superintendence of main roads, public buildings and charitable institutions, and the regulation of weights and measures. The justices were empowered to levy local taxes to support these activities, and in 1739 these were unified as a single "county rate", under the control of a county treasurer. In order to build and maintain roads and bridges, a salaried county surveyor was to be appointed.
By the 1880s it was being suggested that it would be more efficient if a wider variety of functions were provided on a county-wide basis.
Yorkshire had three major subdivisions known as the ridings
Some of the counties had major subdivisions. Of these, the most significant were the divisions of Yorkshire: the East Riding, West Riding, North Riding and the ainsty of York. Since Yorkshire is so big, its ridings became established as geographical terms quite apart from their original role as administrative divisions. The second largest county, Lincolnshire, was divided into three historic "parts": Parts of Lindsey, Holland and Kesteven. Other divisions include those of Sussex into East Sussex and West Sussex and Suffolk into East Suffolk and West Suffolk, and, more informally and hence more vaguely, of Kent into East Kent and West Kent.
Several counties had liberties or sokes within them that were administered separately. Cambridgeshire had the Isle of Ely, and Northamptonshire had the Soke of Peterborough. Such divisions were used by such entities as the Quarter Sessions courts and were inherited by the later administrative county areas under the control of county councils.
Most English counties were subdivided into smaller subdivisions called hundreds. Nottinghamshire, Yorkshire and Lincolnshire were divided into wapentakes (a unit of Danish origin), while Durham, Northumberland, Cumberland and Westmorland were divided into wards, areas originally organised for military purposes, each centred on a castle. Kent and Sussex had an intermediate level between their major subdivisions and their hundreds, known as lathes in Kent and rapes in Sussex. Hundreds or their equivalents were divided into tithings and parishes (the only class of these divisions still used administratively), which in turn were divided into townships and manors. In the 17th century the Ossulstone hundred of Middlesex was further divided into four divisions, which replaced the functions of the hundred. The borough and parish were the principal providers of local services throughout England until the creation of ad-hoc boards and, later, local government districts.