Jefferson is an unincorporated community and census-designated place (CDP) in Frederick County, Maryland, United States. As of the 2010 census the town had a population of 2,111 (which includes the widespread area of the town's zip code, not Jefferson proper). Jefferson was established in 1774 and incorporated as a town in 1831. However, a year later, in 1832, the citizens of the town decided that municipal government was unnecessary, and dis-incorporated the town, which has been unincorporated since then.
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, which was ultimately called "New Town". It contained 40 rectangular lots – 20 aligned on each side of what is now 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, which is today's U.S. Route 340. Along this thoroughfare, wagon traffic and livestock drives were frequent.