In the United States, a county is a geographic subdivision of a state (or federal territory), usually assigned some governmental authority. The term "county" is used in 48 of the 50 states; Louisiana is divided into parishes and Alaska into boroughs. Parishes and boroughs are called "county-equivalents" by the U.S. federal government, as are certain independent cities which are not parts of counties. There are currently 3,143 counties and county-equivalents in the United States. There are 3,033 organized county or county-equivalent governments in the United States according to 2007 Census of Governments.
The powers of counties arise from state law and vary widely. In some states including Connecticut and Rhode Island,  counties are geographic entities, but not governmental jurisdictions. At the other extreme, Maryland counties and the county-equivalent City of Baltimore handle almost all services, including public education, although the state retains an active oversight authority with many of these services.
The average number of counties per state is 62. The state with the most counties is Texas, 254; the state with fewest is Delaware, only three. As of the 2000 Census, average county population was about 100,000. The most populous county is Los Angeles County, California, with estimated population 9,880,000 (2009 Census estimate), greater than all but eight U.S. states. The least populous is Loving County, Texas, with 82 residents as of 2010.
The largest county or county-equivalent is Unorganized Borough, Alaska, more than 330000sqmi. The five largest counties or county-equivalents are all in Alaska; elsewhere the largest by land area is San Bernardino County, California, more than 20000sqmi. The smallest county by land area is Kalawao County, Hawaii, only 13sqmi. With 3,143 counties and 3,794,101 sq miles (2.43 billion acres) in the U.S., the average American county size is approximately 1,207.2 sq. miles (3,126.6 km2). And with a 311.8 million population of the U.S. as of mid 2011, the average population in the 3,143 counties in the U.S. is approximately 99,205 people per county on average, or about 82 people per sq. mile (per 640 acres; per 2.59 km2) on average.
Independent cities such as Baltimore are independent of counties. They differ from consolidated city–counties such as Jacksonville, Florida, New Orleans, Louisiana, Indianapolis, Indiana and San Francisco, California, where a city and county have been merged into one unified jurisdiction. A consolidated city-county is simultaneously a city, which is a municipal corporation (municipality), and a county, which is an administrative division of a state, having the powers and responsibilities of both types of entities.
The site of a county's administration, and often the county courthouse, is called the county seat ("parish seat" or "borough seat" in Louisiana or Alaska). Several Northeastern counties officially use the term "shire town" for the county seat.
Counties were among the earliest units of local government established in the Thirteen Colonies that would become the United States. Virginia created the first counties in order to ease the administrative workload in Jamestown. The House of Burgesses divided the colony first into four "incorporations" in 1617 and finally into eight shires (or counties) in 1634: James City, Henrico, Charles City, Charles River, Warrosquyoake, Accomac, Elizabeth City, and Warwick River. America's oldest intact county court records can be found at Eastville, Virginia, in Northampton (originally Accomac) County, dating to 1632. Maryland established its first county, St. Mary's, in 1637, and Massachusetts followed in 1643. Pennsylvania and New York delegated significant power and responsibility from state government to county governments, and thereby established a pattern for most of the United States, although counties remained relatively weak in New England.
Common sources of county names are names of people, geographic features, places in other states or countries, Native American tribes, and animals. Quite a few counties bear names of French or Spanish origin.
Counties are most often named for people, often political figures or early settlers, with over 2,100 of the 3,140 total so named. The most common county name, with 31, is Washington County, for America's first president, George Washington. Up until 1871, there was a Washington County within the District of Columbia, but it was dissolved by the District of Columbia Organic Act. Jefferson County, for Thomas Jefferson, is next with 27. The most recent president to have a county named for him was Warren G. Harding, reflecting the slowing rate of county creation since New Mexico and Arizona became states in 1912. The most common names for counties named after non-presidents are Franklin (25), Clay (18), and Montgomery (18).
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 countries such as the United Kingdom. The most common geographic county name is Lake. Native American tribes and animals lend their names to some counties. Quite a few counties bear names of French or Spanish origin, such as Marquette County being named after French missionary Father Jacques Marquette.
In many states, the board in charge of a county holds powers that transcend all three traditional branches of government. It has the legislative power to enact ordinances for the county; it has the executive power to oversee the executive operations of county government; and it has quasi-judicial power with regard to certain limited matters (like hearing appeals from the planning commission if one exists).
As for the day-to-day operations of the county government, they are sometimes overseen by a county manager or chief administrative officer who reports to the board, the mayor, or both.
In some states, the county technically has a plural executive in that several important officials are elected separately from the board of commissioners or supervisors (implying they cannot be fired by the board). This can create tension if such officials then disagree on how to best carry out their respective functions.
The power of county governments varies widely from state to state, as does the relationship between counties and incorporated cities. The government of the county usually resides in a municipality called the county seat. However, some counties may have multiple seats or no seat. In some small counties with no incorporated municipalities, a large settlement may serve as the county seat.
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 all others), and most of the governmental authority below the state level is in the hands of towns and cities. In several of Maine's sparsely populated counties, small towns rely on the county for law enforcement, and in New Hampshire several social programs are administered at the state level. In some New England states, such as in Connecticut, parts of Massachusetts, and Rhode Island, counties are now only geographic designations, and they do not have any governmental powers. All government is either done at the state level or at the municipal level. In Connecticut and parts of Massachusetts, regional councils have been established to partially fill the void left behind by the abolished county governments. The regional councils' authority is much more limited compared with a county government - the regional councils have no taxing authority or authority to issue permits; the aforementioned powers are delegated to the town governments. However, the regional councils do have authority 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). The county recorder normally maintains the official record of all real estate transactions. Other key county officials include the coroner/medical examiner, treasurer, assessor, auditor, controller, and district attorney.
In most states, the county sheriff is the chief law enforcement officer in the county. 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.
In virtually all U.S. states, the state courts and local law enforcement are organized and implemented along county boundaries, but nearly all of the substantive and procedural law adjudicated in state trial courts originates from the state legislature and state appellate courts. In other words, most criminal defendants are prosecuted for violations of state law, not local ordinances, and if they, the district attorney, or police seek reforms to the criminal justice system, they will usually have to direct their efforts towards the state legislature rather than the county (which merely implements state law). A typical criminal defendant will be arraigned and subsequently indicted or held over for trial before a trial court in and for a particular county where the crime occurred, kept in the county jail (if he is not granted bail or cannot make bail), prosecuted by the county's district attorney, and tried before a jury selected from that county. But long-term incarceration is rarely a county responsibility, execution of capital punishment is never a county responsibility, and the state's responses to prisoners' appeals is the responsibility of the state attorney general, who has to defend before the state appellate courts the prosecutions conducted by locally-elected district attorneys in the name of the state. Furthermore, county-level trial court judges are officers of the judicial branch of the state government rather than county governments.
In many states, the county controls all unincorporated lands within its boundaries. In states with a township tier, unincorporated land is controlled by the townships. 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 (in states that do not have townships), or village.
A few counties directly provide public transportation themselves, usually in the form of a simple bus system. However, in most counties, public transportation is provided by one of the following: a special district that is coterminous with the county (but exists separately from the county government), a multi-county regional transit authority, or a state agency.
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. They provide services such as child and family services, elder services, mental health services, welfare services, veterans assistance services, animal control, probation supervision, historic preservation, food safety regulation, and environmental health services. They have many additional officials like public defenders, arts commissioners, human rights commissioners, and planning commissioners. Finally, there may also be a county fire department and even a county police department (as distinguished from fire and police departments operated by individual cities, special districts, or the state government). For example, Albemarle County, Virginia, and its county seat, the city of Charlottesville, each have their own police departments. (A separate county sheriff's department is responsible for security of the county courts and administration of the county jail.)
Maryland, in particular, vests its counties with broad powers, including educational responsibilities (which are normally handled in all other states by school districts specific to particular cities, towns, or regions).
There are on average 62.8 counties per state, and median of 62 counties per state as well (including DC), with New York and its 62 counties representing the median for the U.S. (50% of the US states above and below New York's 62 county number). The state with the fewest counties is Delaware (3), though it is unique among the United States in that each Delaware county is divided into units called "hundreds". The state with the most is Texas (254).
Southern and Midwestern states generally tend to have more counties than Western or Northeastern states, as many Northeastern states are not large enough in area to warrant a large number of counties, and many Western states were sparsely populated when counties were created. Connecticut, Massachusetts and Rhode Island have abolished county governments in whole or in part, though the former county territories may be observed in the three states' state-level administrative districts.
|Number of Counties||State||Average County Population Approximately|
|134||Virginia (95 counties and 39 cities),||59,000|
|115||Missouri (114 counties and one city)||52,000|
|24||Maryland (23 counties and one city)||237,000|
|17||Nevada (16 counties and one city)||155,000|
|1||District of Columbia||600,000|
See main article: County statistics of the United States. At the 2000 U.S. Census, the median land area of the 3,077 U.S. counties was 622sqmi, which is only two-thirds of the median land area of a ceremonial county of England, and only a little more than a quarter of the median land area of a French département. However, this figure does not account for the differences among the United States counties themselves; counties in the western United States have a much larger mean land area than those in the eastern United States. For example, the median land area of counties in Georgia is 343sqmi, whereas in Utah it is 2427sqmi.
The largest county equivalent by (total) area is Yukon-Koyukuk Census Area, Alaska, at 147843sqmi, while the largest actual county is San Bernardino County, California, in southern California, which includes the Mojave Desert, at 20105sqmi in area. The second-largest county is Coconino County, Arizona, in the north-central part of the state, which includes the Grand Canyon National Park. The smallest county equivalent is the independent city of Falls Church, Virginia, at 2.2sqmi in area, while the smallest actual county is Kalawao County, Hawaii, at 13sqmi in land area.
At the 2000 U.S. Census, only 16.7% of U.S. counties had more than 100,000 inhabitants. This reflects the essentially rural nature of U.S. counties, whose grid was designed in the 19th century in a country still largely rural, and only marginally affected by urbanization. Today, the vast majority of people in the United States are concentrated in a relatively small number of counties. The most populous county is Los Angeles County, California, with 9,818,605 inhabitants as of 2010, and the least populous county is Loving County, Texas, with 82 inhabitants as of 2010.
The most densely populated county (or county equivalent) is New York County, New York (coextensive with the Borough of Manhattan and consisting of Manhattan Island; Marble Hill, a neighborhood originally on the island but now physically attached to The Bronx; and several small adjacent islands), with 66,940 people per square mile (25,846 per km², or 38.691 square meters per person) as of 2000, and the least densely populated county equivalent is Lake and Peninsula Borough, Alaska, with 0.0767 people per square mile (0.0296 per km², or 33.768 km² per person) as of 2000. The least densely populated county equivalent is Yukon-Koyukuk Census Area, Alaska, with 0.0449 per square mile (0.0173 per km², or 57.683 km² per person) as of 2000.
The term county equivalents includes three additional types of administrative divisions which are different from the type of county found in most states:
These are cities that legally belong to no county. As of 2004, there are 42 such cities in the United States, including Baltimore, Maryland; Carson City, Nevada; St. Louis, Missouri; and all 39 cities in Virginia, where any municipality incorporated as a city (in contrast to town) is by law severed from any county that might otherwise have contained it.
In general, cities, towns, and other municipal governments almost always occupy a smaller area than the county which contains them, and they sit only in that county (that is, they are prohibited from annexing territory in more than one county). However, there are exceptions: