Charlestown is a city in Clark County, Indiana, United States. The population was 7,585 at the 2010 census.
Charlestown was established in 1808, named after one of its surveyors, Charles Beggs, upon 300 acres (1.2 km2), of which 3 acres (12,000 m2) was designated for a town square. It was established one mile (1.6 km) northeast of Springville, and was responsible for Springville's demise.
Milling was important to the town, as the first mill was built in the area, on Fourteen Mile Creek, in 1804. This mill would be abandoned when John Work built a mill by use of a tunnel in 1814. Today, that mill is part of the Tunnel Mill Scout Reservation.
From 1811 to 1878 Charlestown was the county seat of Clark County, but as Jeffersonville had surpassed it economically, the county seat reverted to Jeffersonville in 1878.
In 1818 the first Grand Lodge of Free & Accepted Masons in Indiana met in Charlestown, due to Jonathan Jennings' influence.
In 1940 the population of Charlestown was 900, but it swelled to 13,400 due to the building and operation of the Indiana Army Ammunition Plant (INAAP).