The land west of the Oconee River was organized as Baldwin and Wilkinson counties. The Treaty of Washington with the Creek in 1805 extended the state's western boundary to the Ocmulgee River. A legislative act on June 26, 1806, added some of this additional land to both counties.
The state legislature subsequently passed an act on December 10, 1807 that created four new counties from Baldwin County's 1806 borders. It expanded Baldwin to the east with land from Hancock and Washington counties. The new counties were Morgan, Jones, Putnam, and present-day Jasper (originally named Randolph County at the time of the act).
The county is named for Abraham Baldwin, a signer of the United States Constitution, U.S. congressman representing Georgia, and the founder of the University of Georgia. White settlers moved into the area and developed large cotton plantations, made possible by the labor of slaves. Since the invention of the cotton gin, short-staple cotton could be profitably processed, and it was well-suited to the uplands of Georgia. What became known as the Black Belt of Georgia, an arc of fertile soil, was one of the destinations for slaves being sold from the Upper South, as well as from the Low Country.
The county seat of Milledgeville is the former state capital of Georgia (1804–1868). Other than Washington, DC, it is the only planned capital city in the United States.
Because of its central location within the state and its abundant supply of water from the Oconee River, Milledgeville grew rapidly into a bustling frontier town. On November 2, 1807, the state legislature held its first session in the newly completed statehouse in Milledgeville. Georgia's first state penitentiary was also built within the historic city limits of Milledgeville in 1817. This site is now used as the main campus of Georgia College and State University. In 1837 the General Assembly provided for the establishment of the state's first mental asylum, today known as Central State Hospital.
Putnam County, Georgia - north
Hancock County, Georgia - northeast
Washington County, Georgia - east
Wilkinson County, Georgia - south
Jones County, Georgia - west