Fincastle County, Virginia, was created in 1772 from Botetourt County, the boundaries of which extended all the way to the Mississippi River. Fincastle County was abolished in 1776, and divided into three new counties--Montgomery County, Washington County, and Kentucky County (which in 1792 became the 15th state, the Commonwealth of Kentucky)--by action of the Virginia General Assembly.
Although no county seat was designated by the act creating the county, the colonial governor ordered it to be placed at the "Lead Mines" of Wythe County, where Austinville, Virginia, is now located.
Botetourt County may have been named for the English home of Norborne Berkeley, 4th Baron Botetourt, a very popular governor of the Colony of Virginia, who died just before the tensions of the impending American Revolution made the job much more difficult. John Murray, Earl of Dunmore and Viscount of Fincastle, succeeded Lord Botetourt. Fincastle County may have been named in his honor, or for his son Lord Fincastle. If so, the decision to change the name in 1776 is very logical. At that time, Lord Dunmore was leading the military opposition to the rebels in Virginia, and had already issued Dunmore's Proclamation offering to free any slaves who fled their Virginia masters and joined the royal British forces.