The parish was from the Middle Ages until late in the nineteenth century the basic territorial unit in the organisation of this country. During the Middle Ages there were in England alone some 8,500 parishes, but their number must remain uncertain for any period before the seventeenth or eighteenth century. Their geographical pattern was fluid, as large parishes broke up and smaller and poorer merged with their neighbours. In origin the parish was a unit of ecclesiastical administration and pastoral care. It was an area large enough in population and resources to support a church and its priest, and yet small enough for its parishioners to gather at its focal church. Yet this ideal was difficult to achieve and impossible to sustain.

A system of parishes had begun to evolve during the middle Anglo-Saxon period, and by the end of the twelfth century it had been extended over most of the country. Since then the only alterations have been those induced by a changing pattern of wealth and population. When they first emerged, parishes reflected the distribution of settlement and the structure of society.