The city of Carmi was founded in 1814, and incorporated in 1816. White County was organized from Gallatin County in 1815, and was named after Captain Leonard White, a Gallatin County legislator who is credited with the idea of extending the Illinois-Wisconsin border a few miles north of the southern tip of Lake Michigan. The first courthouse was in the cabin of John Craw.

Other early settlements were Grayville, located at the mouth of Bonpas Creek and the (Big) Wabash River, settled by the Gray family around 1810, Phillipstown, on the bluffs above the Wabash and Fox River floodplain, and New Haven (mostly in Gallatin County), which was home to a brother of Daniel Boone around 1818. Old Sharon Church (Presbyterian), located near the later village of Sacramento, was organized around 1816, and the village of Seven Mile Prairie was established a few miles north of the church in the 1830's. The parents of Ann Rutledge were part of this group, along with families named McArthy, Miller, McClellan, Storey, Fields, and Johnson.

About 1839, a group of Irish immigrants began moving into the extreme western part of Enfield Township, led by Patrick Dolan, as well as members of the Mitchell and Dunn clans. Dolan was auctioneer in 1853 when the village of Enfield was platted, as Seven Mile moved west in anticipation of a railroad line, which was not built until 1872. German families moved into the middle portion of the county in the 1840s and onward, especially from the Baden region, and included the family names of Rebstock, Dartt, Brown, Sailer, Stanley, and Drone.

The second half of the 19th century saw the establishment of the towns of Norris City, Springerton, Mill Shoals (once the home of a thriving barrel-making industry which depleted the nearby virgin forests), Epworth, Herald, Burnt Prairie, Crossville, Phillipstown, Concord (also known as Emma), Maunie and Rising Sun (commonly called Dogtown)--the latter two villages are located on the Wabash and attracted several African-American families. A number of villages which no longer exist were also formed: Trumbull, Roland, Middle Point, Stokes Station, Gossett, Bungay, Calvin, Iron, and Dolan Settlement.

Agriculture was the primary industry of White County until the summer of 1939, when oil was discovered in the Storms and Stinson fields in the Wabash River Bottoms. The population of Carmi doubled within two years, from 2,700 to 5,400, with corresponding increases at Crossville and Grayville--in 1940 it was said one could walk between these two towns by simply walking from rig to rig. Many of these workers migrated from previous oil booms in Texas and Oklahoma.

The current population of White County is a little over 17,000, with 6,500 in the county seat of Carmi. There is a high number of retired people, and many citizens work in the factories of Evansville or Mt. Vernon, Indiana, located 45 and 25 miles to the east, respectively. Besides oil and agriculture, industries include auto parts manufacturing, plastics, a convenience store distribution center, and underground coal mining.