Jefferson is older than Marengo County and the State of Alabama. It was founded in 1810, and most of its first settlers were veterans of the American Revolution, among them John Sample, John Gilmore and Reuben Hildreth. The village took the name Jefferson, for Thomas Jefferson, in 1820.
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That same year Elder James Yarbrough organized the community's first church, Mt. Pleasant Baptist, now Jefferson Baptist Church, with 27 charter members; by 1834 it had 150 members, and it is among the oldest churches in the Demopolis area. Sample, Gilmore and Hildreth are buried in its cemetery.
By 1860 Jefferson had about 200 residents, two dry goods stores, a drugstore, academies for boys and girls, a Masonic lodge, a hotel, two tanneries, a wagon shop and a blacksmith shop. The 1870 census counted 233 residents. Today Jefferson is a small unincorporated community.
Sources
The Historical Marker Database: Jefferson Baptist Church (Alabama Historical Association)
Wikipedia: Jefferson, Alabama