The Frederick Historic District is a national historic district in Frederick, Maryland. The district encompasses the core of the city and contains a variety of residential, commercial, ecclesiastical, and industrial buildings dating from the late 18th century to 1941. Notable are larger detached dwellings in the Queen Anne and American Foursquare architectural styles of the late 19th and early 20th centuries The churches reflect high style architecture ranging from Gothic and Greek Revival to Richardsonian Romanesque and Colonial Revival. The east side of the district includes the industrial buildings. It was added to the National Register of Historic Places in 1973, with a boundary increase in 1988.