[3] The term "county" is used in 48 states, while Louisiana and Alaska have functionally equivalent subdivisions called parishes and boroughs, respectively.

[3] Counties and other local governments exist as a matter of U.S. state law, so the specific governmental powers of counties may vary widely between the states, with many providing some level of services to civil townships, municipalities, and unincorporated areas.

Louisiana parishes, the organized boroughs of Alaska, independent cities, and the District of Columbia are equivalent to counties for administrative purposes.

Alaska's Unorganized Borough is further divided into 11 census areas that are statistically equivalent to counties.

The U.S. Census Bureau counts American Samoa's districts and atolls as county equivalents.

Virginia created the first counties in order to ease the administrative workload in Jamestown.

[15] In the twentieth century, the role of local governments strengthened and counties began providing more services, acquiring home rule and county commissions to pass local ordinances pertaining to their unincorporated areas.

[14] In 1955, delegates to the Alaska Constitutional Convention wanted to avoid the traditional county system and adopted their own unique model with different types of boroughs varying in powers and duties.

Similarly, some of Alaska's boroughs have merged with their principal cities, creating unified city-boroughs.

Quite a few counties bear names of Native American, French, or Spanish origin.

After people, the next most common source of county names are geographic features and locations, with some counties even being named after counties in other states, or for places in other countries, such as the United Kingdom (the latter is most common in the area of the original Thirteen Colonies in the case of the United Kingdom, or in places which had a large number of immigrants from a particular area for other countries).

Before the Louisiana Purchase and granting of statehood, government was often administered in towns where major church parishes were located.

In many states, the board in charge of a county holds powers that transcend all three traditional branches of government.

[37] In Connecticut and Rhode Island,[38][39] counties are geographic entities, but not governmental jurisdictions.

[41] In most Midwestern and Northeastern states, counties are further subdivided into townships or towns, which sometimes exercise local powers or administration.

In New England, counties function at most as judicial court districts and sheriff's departments (presently, in Connecticut only as judicial court districts—and in Rhode Island, they have lost both those functions and most others but they are still used by the United States Census Bureau and some other federal agencies for some federal functions), and most of the governmental authority below the state level is in the hands of towns and cities.

In Connecticut, Rhode Island, and parts of Massachusetts, counties are now only geographic designations, and they do not have any governmental powers.

In Connecticut and parts of Massachusetts, regional councils have been established to partially fill the void left behind by the abolished county governments.

[e] The regional councils' authority is limited compared with a county government—they have authority only over infrastructure and land use planning, distribution of state and federal funds for infrastructure projects, emergency preparedness, and limited law enforcement duties.

In the Mid-Atlantic and Midwest, counties typically provide, at a minimum, courts, public utilities, libraries, hospitals, public health services, parks, roads, law enforcement, and jails.

There is usually a county registrar, recorder, or clerk (the exact title varies) who collects vital statistics, holds elections (sometimes in coordination with a separate elections office or commission), and prepares or processes certificates of births, deaths, marriages, and dissolutions (divorce decrees).

Other key county officials include the coroner/medical examiner, treasurer, assessor, auditor, comptroller, and district attorney.

However, except in major emergencies where clear chains of command are essential, the county sheriff normally does not directly control the police departments of city governments, but merely cooperates with them (e.g., under mutual aid pacts).

Thus, the most common interaction between county and city law enforcement personnel is when city police officers deliver suspects to sheriff's deputies for detention or incarceration in the county jail.

Residents of unincorporated land who are dissatisfied with county-level or township-level resource allocation decisions can attempt to vote to incorporate as a city, town, or village.

A few counties directly provide public transportation themselves, usually in the form of a simple bus system.

In western and southern states, more populated counties provide many facilities, such as airports, convention centers, museums, recreation centers, beaches, harbors, zoos, clinics, law libraries, and public housing.

In several southern states, public school systems are organized and administered at the county level.

The least extensive county equivalent in the 50 states is the independent city of Falls Church, Virginia, with a land area of 1.999 square miles (5.177 km2).

[3] If U.S. territories are included, the least extensive county equivalent is Kingman Reef, with a land area of 0.01 square miles (0.03 km2).