Formed 18 Feb 1805, 549 square miles
Parent counties: Ross, Adams, Clermont
Evolution of county from date of formation until it assumed its final form
1 May 1805: Erected and organized
1 Mar 1834: Part attached to Ross
12 Mar 1845: Part of Athens attached
23 Mar 1850: Diminished by formation of Vinton. Parts of Athens and Fairfield attached
From 1805-1807, New Market was the county seat of Highland County. In 1807, the county seat was transferred to Hillsboro.
Federal Population schedules extant from 1820-1940. (1890 missing)
1820 Manufacturers; 1850 Agricultural; 1850 Industry; 1850 Mortality; 1860 Agricultural; 1860 Mortality; 1870 Agricultural; 1870 Industry; 1880 Agricultural; 1880 Defective, Dependent, and Delinquent
Brush Creek, Clay, Concord, Dodson, Fairfield, Hamer, Jackson, Liberty, Madison, Marshall, New Market, Paint, Penn, Salem, Union, Washington, and White Oak.
Jana Broglin, OGSF