Gallatin County started off with salt processing at the Saline Spring and Half Moon Lick. The salt industry became the primary industry of the county and the state. When Illinois entered the union in 1818 it was to enter the Union as a free state as established by the Northwest Ordinance. An exception to the exclusion of slavery was made in the Illinois Constitution for the area known as the Gallatin Salines. The growing new state needed the revenue from the salt wells.
By 1812 the federal government had created the Shawneetown Land Office. Gallatin County was officially organized that year. It was the second county in the state after St. Clair county. Out of the county grew the present day counties of Saline, White, Franklin, Hamilton, Hardin, and parts of Pope and Williamson.
After the 1937 flood of the Ohio River, Shawneetown was moved to a new location. Property there was recorded by Johnathan Boone, a brother of Daniel Boone. By the time Illinois became a state in 1818 the county was booming, it was the point of entry into the new land. The Ohio river provided easy access to this “Wild West.”