The commercial core of Frederick is concentrated along Market and Patrick Streets.  The scale of these commercial buildings is generally consistent with their surroundings; rarely do they exceed four stories in height.  In form, they are two-part blocks, featuring a street level which is clearly differentiated from the upper section.  The street level usually comprises a storefront with large display windows.  Like their residential neighbors, the decorative detailing of these commercial buildings reflect a wide variety of popular styles of the late 19th and early 20th centuries.  Many of the commercial buildings in the Frederick Historic District represent conversions of originally-residential structures.

Several commercial buildings reflect modern design trends of the turn of the 20th century, as metal-frame construction methods made possible large window areas on upper stories.  These include 36 South Market Street, a four story building with a prefabricated iron facade, and the building on the Northwest corner of Market and Patrick Streets, which features broad window openings characteristic of the early-20th-century "Commercial Style".  In addition, there are several noteworthy Neoclassical Revival bank buildings, whose detailing lends a sense of monumental stability despite their relatively small scale.