Jefferson is an unincorporated community and census-designated place (CDP) in Frederick County,Maryland, United States. As of the 2010 census it had a population of 2,111.
According to archaeologist Mary F. Barse, Jefferson was initially laid out in 1774 on a 96-acre (390,000 m2) tract owned by Mrs. Eleanor Medley and called "New Town". It contained 40 rectangular lots – 20 aligned on each side of MD 180 – stretching between what are now Lander Road and Old Middletown Road. In 1795, 22 additional lots were platted by Elias Delashmutt on the western end of the original section, and called "New Freedom". In 1831 both sections were incorporated as "Jefferson" by the Maryland Legislature. Jefferson's growth in the 19th century was due largely to its location on the main road between Frederick and Harpers Ferry, today's U.S. Route 340. Wagon traffic and livestock drives were frequent. Concomitantly, commercial development intensified to serve the surrounding farms as well as travelers. As a center of agricultural mercantilism, throughout most of the late 18th and 19th century Jefferson was also home to a sizable population of slaves