On that date residents approved alcohol sales for off-premises consumption, making it a "wet" county.

[4] Like most of the Jackson Purchase, and reflecting its geographic and family connections to the South, during the American Civil War, Marshall County was strongly pro-Confederate, although the state was neutral.

In the 1940s, however, the Tennessee Valley Authority created Kentucky Lake as part of its flood control and rural electrification projects initiated by President Franklin D. Roosevelt.

The lake established tourism as part of the county's economy, and lakeshore resorts were developed to exploit sports fishing.

Kentucky Dam's cheap and plentiful electricity also attracted chemical and manufacturing plants, mainly in the Calvert City area.

The lake's impoundment resulted in flooding two historic Marshall County towns: Birmingham, six miles north of Fairdealing, and Gilbertsville, at the dam's site, both of which were evacuated.

Tater Day derives its name from the main item traded—sweet potatoes for seed, i.e., for bedding in prepared "seedbeds" to produce slips for growers to transplant to gardens or fields.

On the fourth Sunday of each May, The Big Singing, an all-day sing-along program of Southern Harmony shape note gospel music is held at the county courthouse.

The Big Singing, begun in 1884, has a special claim to fame: in 1933 George Pullen Jackson drew attention to the fact that this is the only regular event that sings from William Walker's Southern Harmony;[13] this remains a living tradition to the present day.

[14] Marshall County is the home of Calvert Drive In Theater, the only one in the Purchase area and one of three within an 85-mile radius in far western Kentucky.

"[17] Before Interstate 24 rerouted much of US 68 traffic northward, generations spent summer days and nights at The Forgotten Past Amusement Park with its gift shop, go carts, bumper cars, mini golf, museum, and arcade.

It is built upon land donated from a private family in memory of their son who was killed in action in the Vietnam War.

[19] Marshall County is home to the FLW Bass Tournament organization, named for founder of Ranger Boats, Forrest L. Wood.

In 2015, all elected county officials were Democrats, except for one: Republican Kevin Neal defeated Melonie Watkins Chambers to finish the unexpired term of longtime County Judge-Executive Mike Miller, who died in office the previous December.