Boonsboro is a town in Washington County, Maryland, United States, located at the foot of South Mountain. It nearly borders Frederick County and is proximate to the Antietam National Battlefield. The population was 3,336 at the 2010 census.
Local lore asserts Boonsboro was founded by George Boone, a cousin of Daniel Boone, and was originally named "Margaretsville" after his wife. The town was incorporated as Boonesborough in 1831. Local newspapers and villagers preferred the name Boonsboro. The former name was used on some documents as late as 1903.
Boonsboro was a key town during the American Civil War. Two battles were fought in its present borders. The town was also used to keep wounded soldiers after the Battle of Antietam in September 1862.