West Virginia has 55 counties, created from 1754 to 1895. Randolph County is the largest, at 1,040 square miles, and Hancock the smallest, at 88.2 square miles. Kanawha County has the most people, with 180,745 residents in 2020, and Wirt has the fewest, 5,194.

West Virginia inherited the county system of local government from Virginia, and 50 of West Virginia's counties were created before the two states separated. Virginia counties, in turn, were patterned after those of England, where counties date back more than a thousand years. West Virginia experimented with a modified township system in its original 1863 constitution, but the constitution adopted in 1872 and still in force today reverted to the Virginia model. All West Virginia counties descend from two counties of Virginia, Frederick and Augusta, created in 1743 and 1745, respectively, and named for the prince and princess of Wales.

The great majority of West Virginia counties were created between the late 18th and the late 19th centuries. The early exception was Hampshire, West Virginia's oldest county, created in 1754. Berkeley, West Virginia's other colonial-era county, was created in 1772. Ohio and Monongalia counties were created in a single act of legislation in 1776, the first year of American independence, along with Yohogania, a phantom county whose territory was later lost to Pennsylvania in a boundary resolution. A total of 13 counties were established in the 18th century.

The most fruitful period of county formation was the quarter-century preceding the Civil War, when nearly half of West Virginia counties appeared. These years saw the filling out of the settlement pattern, with nearly all parts of the present state fully occupied by 1861. New counties were established to provide convenient access to government, the ideal said to have been no more than a day's ride by horseback from any citizen's home to the county courthouse.

The status of two counties, Jefferson and Berkeley, remained uncertain when West Virginia was formed in 1863. Their inclusion in the new state was confirmed by the U.S. Congress in 1866 and the U.S. Supreme Court in 1871. Very early maps of West Virginia omit these easternmost counties, with the Eastern Panhandle ending abruptly at Morgan County. Only one county, Frederick, voted not to become part of West Virginia when offered the opportunity. It remains within the boundaries of Virginia.

Five counties were created after West Virginia became a state, four of them within a decade of the end of the Civil War. Two of the new counties, Lincoln and Grant, were named for heroes of the war. A third, Mineral, was created in part due to wartime differences in mother Hampshire County, the people in the mountainous western territory that became the new county having favored the Union to a greater extent than did the residents of the eastern river valleys who remained Hampshire Countians.

Mingo, the youngest West Virginia county, was carved from Logan County in 1895, and named for Chief Logan's people, the Mingo tribe.

As in other parts of rural America, in West Virginia the county is the unit of government to which many citizens feel most closely attached. Candidates contend vigorously to be sheriff or county commissioners, and occasional "courthouse wars" have broken out over the location of the county seat. The county seat of Jefferson traveled from Charles Town to Shepherdstown and back again in the bitter aftermath of the Civil War, for example, and in 1893 the Tucker County records were stolen away from St. George before the legal transfer of the county seat to Parsons. Every West Virginia county has a colorful story, many of which have been recorded in excellent books of county history.