Marshall County is a county located in the U.S. state of Kentucky. As of 2000, the population was 30,125. The 2007 Census Bureau population estimate was 31,258. Its county seat is Benton. It was a dry county until 2004, when residents of Calvert City voted to allow sales of liquor by the drink in restaurants. It is the only Purchase Area county to not border another state.
The county was formed in 1842 from part of Calloway County. The first settlement was around 1818, when the area was bought from Native Americans as part of the Jackson Purchase. Marshall County was named in honor of Chief Justice John Marshall, who had died not long before the founding of the county.
From its settlement until the 1930s, the county was nearly completely agricultural.
The creation of Kentucky Lake by the Tennessee Valley Authority in the 1940s brought tourism and industry to the county with resorts along the lake. The Kentucky Dam's cheap and plentiful electricity also attracted chemical and manufacturing plants, mostly in the Calvert City area. The creation of the lake led to the destruction of two Marshall County towns: Birmingham, located about six miles north of the present day town of Fairdealing, and Gilbertsville, which was at the present-day dam site. Gilbertsville was rebuilt somewhat to the west of its original location. Birmingham residents were dispersed. Gilbertsville was an incorporated town until the 1970s, when its charter was dissolved by public vote. Kentucky Lake (created by the impounding of the Tennessee River) and Lake Barkley (created through the impounding of the Cumberland River) make up one of the largest man-made bodies of water in the world.
Historically, Marshall County has been a stronghold of the Democratic Party. Since the founding of the county, Democrats have dominated county politics. Today, all elected county officials are Democrats, with the exception of one.