Alexandria is a city in eastern Clark County, Missouri, United States. As of the 2020 census, its population was 105. Alexandria is part of the For…Alexandria is a city in eastern Clark County, Missouri, United States. As of the 2020 census, its population was 105. Alexandria is part of the Fort Madison-Keokuk micropolitan area. Alexandria was founded in the 1830s. The community was named after John Alexander, the proprietor of a nearby ferry. A post office called Alexandria has been in operation since 1840.