The county was formed in 1752 from parts of Bladen County, Granville County, and Johnston County. It was named for the infant William V of Orange, whose mother Anne, daughter of King George II of Great Britain, was then regent of the Dutch Republic.
In 1771 Orange County was greatly reduced in area. The western part of it was combined with the eastern part of Rowan County to form Guilford County. Another part was combined with parts of Cumberland County and Johnston County to form Wake County. The southern part of what remained became Chatham County.
In 1777 the northern half of what was left of Orange County became Caswell County. In 1849 the western third of the still shrinking county became Alamance County. Finally, in 1881 the eastern half of the county's remaining territory was combined with part of Wake County to form Durham County.
According to the U.S. Census Bureau, the county has a total area of 401 square miles (1,040 kmē), of which, 400 square miles (1,036 kmē) of it is land and 1 square miles (4 kmē) of it (0.34%) is water.
The county is drained, in part, by the Eno River.
Notable residents:
* Thomas Samuel Ashe, United States Congressman from North Carolina
* John Edwards, former North Carolina Senator, 2008 Presidential candidate
* Doug Marlette, cartoonist and writer
* Archibald Murphey, North Carolina politician
* Beverly Perdue, North Carolina lieutenant governor
* David Price, U.S. congressman
* Lee Smith, author
* Connie Ray, actress and playwright
* Joseph H. Johnston, WWI veteran, Distinguished Service Cross awardee (posthumously)
