Adamstown is an unincorporated community and census-designated place (CDP) in Frederick County, Maryland, United States.

It is named for Adam Kohlenberg (March 11, 1819 – January 1, 1868), a station agent and first town merchant who owned much of present-day Adamstown.

It is significant in architecture for its variety of structures, including residential, commercial, industrial, educational, agricultural, and religious buildings.

Adamstown was first known as "Davis' Warehouse" because Dr. Meredith Davis, a leading Quaker county miller, built a warehouse about 1835 where Mountville Road, by then called Jefferson Road, crossed the Baltimore and Ohio Railroad (9 miles (14 km) southwest of Frederick) to store flour from his Greenfield Mills.

Daniel Rhodes of Pennsylvania, the first white settler, was so impressed with the location, he bought a tract of land and laid it off into 12 building lots on the south side of the railroad in 1856.

With Adamstown located close to the Potomac River and Virginia, its citizens were almost exclusively loyal to the South during the Civil War; however, both Federal and Confederate troops were constantly moving on Carrollton Manor.

For several months in the spring of 1861, the Minute Men of Adamstown, a secession militia company composed of three officers (Captain Robert H. E. Boteler, 1st Lieutenant Jacob G. Thomas, and 2nd Lieutenant William Hilleary Johnson, all local doctors) planted a pole and flew the Confederate flag adjacent to their guard post next to the B&O railroad.

Many skirmishes in the war were fought here and the town was often raided, most notoriously by the 43rd Battalion Virginia Cavalry, also known as Mosby's Rangers, on July 30 and October 14, 1864.