Decatur, the county seat of DeKalb County, is the oldest city in the county. Decatur was designated county seat on December 10, 1823, and named after Stephen Decatur, a U.S. Naval hero.
In historic Decatur, the Old Courthouse on the Square, is a restored 1898 courthouse that also houses the 1500 volume archives, a museum on DeKalb County and Civil War exhibits.