What is County?

Legal Definition
A county is a geographical region of a country used for administrative or other purposes, in certain modern nations. The term is derived from the Old French conté or cunté denoting a jurisdiction under the sovereignty of a count (earl) or a viscount. The modern French is comté, and its equivalents in other languages are contea, contado, comtat, condado, Grafschaft, graafschap, Gau, etc. (cf. conte, comte, conde, Graf).

When the Normans conquered England, they brought the term with them. The Saxons had already established the districts that became the historic counties of England, calling them shires (many county names derive from the name of the county town (county seat) with the word "shire" added on: for example, Gloucestershire and Worcestershire).

The Vikings introduced the term earl (from Old Norse, jarl) to the British Isles. Thus, the Anglo-Saxon's "earl" and "earldom" were taken as equivalent to the continental use of "count" and "county" under the conquering Normans, and over time the two blended and became equivalent terms. Further, the later-imported term became a synonym for the native English word scir ([ʃiːr]) or, in Modern English, shire. Since a shire was an administrative division of the kingdom, the term "county" evolved to designate an administrative division of states (federal states like those of Germany and the United States) or of a national government in most other modern uses.

In the United States and Canada, founded on the British traditions 700 years later counties are usually an administrative division set by convenient geographical demarcations, which in governance have certain officeholders (e.g. Sheriffs and their departments) as a part of the state/province mechanisms, including geographically common court systems.

A county may be further subdivided into districts, hundreds, townships or other administrative jurisdictions within the county. A county usually, but not always, contains cities, towns, townships, villages, or other municipal corporations, which in most cases are somewhat subordinate, or dependent upon county governments. Depending on the nation and the municipality and local geography, municipalities may or may not be subject to direct or indirect county control—the functions of both levels are often consolidated into a city government when the area is densely populated.

Outside English-speaking countries, an equivalent of the term "county" is often used to describe sub-national jurisdictions that are structurally equivalent to counties in the relationship they have with their national government; but which may not be administratively equivalent to counties in predominantly English-speaking countries.
-- Wikipedia
Legal Definition
A district into which a state is divided.

2. The United States are generally divided into counties; counties are divided into townships or towns.

3. In Pennsylvania the division of the province into three Counties, viz. Philadelphia, Bucks and Chester, was one of the earliest acts of William Penn, the original proprietary. There is no printed record of this division, or of the original boundaries of these counties. Proud says it was made about the year 1682. Proud's Hist. vol. 1) p. 234 vol. 2, p. 258.

4. In some states, as Illinois; 1 Breese, R. 115; a county is considered as a corporation, in others it is only a quasi corporation. 16 Mass. R. 87; 2 Mass. R. 644 7 Mass. R. 461; 1 Greenl. R. 125; 3 Greenl. R. 131; 9 Greenl. R. 88; 8 John. R. 385; 3 Munf. R. 102. Frequent difficulties arise on the division of a county. On this subject, see 16 Mass. R. 86 6 J. J. Marsh. 147; 4 Halst. R. 357; 5 Watts, R. 87 1 Cowen, R. 550; 6 Cowen, R. 642; Cowen, R. 640; 4 Yeates, R. 399 10 Mass. Rep. 290; 11 Mass. Rep. 339.

5. In the English law this word signifies the same as shire, county being derived from the French and shire from the Saxon. Both these words signify a circuit or portion of the realm, into which the whole land is divided, for the better government thereof, and the more easy administration of justice. There is no part of England that is not within some county, and the shire-reve, (sheriff) originally a yearly officer, was the governor of the county. Four of the counties of England, viz. Lancaster, Chester, Durham and Ely, were called counties Palatine, which were jurisdictions of a peculiar nature, and held by, especial charter from the king. See stat. 27 H. VIII. c.25.
-- Bouviers Law Dictionary
Legal Definition
The name given to the prin--cipal subdivisions of the kingdom of England and of most of the states of the American Union, denoting a distinct portion of territory organized by itself for political and judicial purposes. The etymology of the word shows it to have been the district anciently governed by a count or carl. In modem use, the word may denote either the territory marked off to form a county or the citizens resident within such territory, taken collectively and considered as invested with political rights or the county regarded as a municipal corporation possessing subordinate governmental powers or an organized jural society invested with specific rights and duties. Patterson v. Temple, 27 Ark. 207; Eagle v. Beard, 33 Ark. 501; Wooster v. Plymouth, 62 N. H. 208.
-- Black's Law Dictionary