Leonardtown is a town in and the county seat of St. Mary's County, Maryland, United States. The population was 2,930 at the 2010 census.
Records indicate that by 1654, county court was conducted at the house of John Hammond in the area known as "Newtown" or "Newtowne Hundred". During the late 17th century, it appears that court was held at various homes throughout Newtown, and that it wasn't until 1708 that an official town with a designated courthouse was established. It was during this same year that Phillip Lynes, then Mayor of St. Mary's City, Maryland's Colonial Capital, designated fifty acres of land at the head of "Brittons Bay" to be divided into 100 lots. He further ordered that one lot be set aside for a county courthouse to be built at an expense not to exceed 12,000 pounds of tobacco. At this time, Newtown was promptly renamed Seymour Town in honor of Governor John Seymour. Nearly 20 years later, Seymour Town was renamed again to Leonard Town in honor of Benedict Leonard Calvert, who was Maryland's Governor during this period. In the decades that followed, Leonard Town became the place where local residents conducted their official business with the colony. Farm products were regularly shipped through the port. Historic Leonardtown remains the only incorporated municipality in St. Mary's County with its own elected Mayor and Town Council. The Town is experiencing a renaissance of its downtown as witnessed by recent openings of several new restaurants and businesses, some of which are located in historic buildings. The town is currently being revitalized starting with the transformation of the Leonardtown Wharf at the foot of Washington Street into a public waterfront park along with the inclusion of a mix of retail shops, office space, a first-class hotel, and residential units. Facilities for boating, kayaking and canoeing are also planned. The Naval Air Base located at Patuxent River has boosted the economy in Leonardtown largely. Many families have relocated to Leonardtown as a result of the base.