In 1810, the county was named for Col. William Grayson, who lived from 1740 to 1790 and served as aide-de-camp to Gen. Washington. He was a lawyer; served in the Revolutionary Army from 1776 to 1779; on the Board of War from 1780 to 1781; in the Virginia Assembly and Continental Congress from 1784 to 1787; in the State Convention ratifying the Federal Constitution in 1788; and in the first U. S. Senate from 1789 to 1790. Washington once owned 5,000 acres in the county, which was formed from Hardin and Ohio counties.