City limits or city boundaries refer to the defined boundary or border of a city. The area within the city limit can be called the city proper. Town limit/boundary and village limit/boundary apply to towns and villages. Similarly, corporate limit is a legal name that refers to the boundary of municipal corporations. In some countries, the limit of a municipality may be expanded through annexation.
United Kingdom
In the UK, city boundaries are more difficult to define, since British cities are defined as any town or local authority area, regardless of area or population size, that has been granted letters patent as a royal prerogative. In smaller cities, such as Wells (pop. approx. 10,000) or Gloucester (pop. approx. 100,000), the boundary will be that governed by the city council, though in certain cases such as Carlisle, this may include large rural and even uninhabited areas which are largely distinct from the main settlement. In the case of larger cities, such as Birmingham (pop. approx. 1,000,000), local government will be administered by a metropolitan borough but the wider metro area may also have a county or regional combined authority. London, the largest city, is the original model for this in the UK: almost all of the metropolitan area (known as Greater London) is governed by the Greater London Authority. However, as a regional administration its powers are limited, and the 32 boroughs plus the ancient City of London contained within it are responsible for the majority of services to citizens.
Although British city (or borough) boundaries are often important for defining local services such as refuse collection and planning (zoning), in most places they form a low level local government. Law enforcement, education and other services are generally defined by county boundaries (or larger areas), and central government is responsible for the National Health Service (NHS Scotland or NHS Wales outside of England).
Planning (zoning) law around British cities is generally determined by green belt laws, which prevent building on the countryside surrounding large and medium-sized towns and cities.
Property within a city limit is subject to city taxation and city regulation, and expects city services. Areas outside any city's limit are considered to be unincorporated, and in most U.S. states they are by default regulated and taxed by the county. In others, areas outside a city's limit fall within another type of local government, such as the civil township (a division of a county). Cities and towns may have extraterritorial jurisdiction beyond their limits, typically for zoning purposes. The distance this extends varies based on the population or area of the city, or which "class" it is considered to be under state law.
A city's limit may extend into more than one county, which can complicate certain matters of policing and taxation. (For example, sales tax revenue collected in a city by one county may not be spent in another part of the city outside that county.) Where a city merges its government with that of its county to become a consolidated city-county, the city limit is usually considered to be expanded to occupy all of the previously unincorporated area of the county, while other existing municipalities continue to exist but are permanently locked into their city's limit without the possibility of annexation (except possibly into a neighboring county). An independent city's limit separates it from being in any county at all. Similarly, cities and towns may or may not be considered part of the township[s] they are in.
City, town, and village limits are not usually coterminous with post office locations or ZIP codes, and the USPS even considers some places to be "unacceptable" for use on mail. (For example, parts of Sandy Springs within its city limit but outside 30328 must use "Atlanta, GA" instead.) School districts and other special-purpose districts may be overlaid on cities, or cities may choose to have their own — however, these are often under other authorities.
A Town's limit was often a radius from a train depot, and several still remain this way.