Ohio County, Indiana: History
Dearborn County was formed from Indiana Territory in 1803, and its borders were modified several times, both before and after the creation of the state of Indiana in 1816. Ohio County was created out of Dearborn County, authorized by legislative action effective January 4, 1844, to resolve a dispute of county seat between Rising Sun and Lawrenceburg. It was named for the Ohio River, which defines its eastern border.
The Ohio County courthouse was built in the county seat of Rising Sun in 1845. It is a two-story Greek Revival brick building measuring about 60 feet (18 m) by 40 feet (12 m), including the portico supported by Doric pillars. This courthouse is still in use and is the oldest continuously used courthouse in the state.