The Central Catonsville and Summit Park Historic District is bounded on the north by Frederick Road, an east-west thoroughfare that was originally a Turnpike from Baltimore to Frederick, an on which the village of Catonsville grew up to the east. The north side of Frederick Road marks the southern boundary of the Old Catonsville Historic District. The western and southern boundary, Rolling Road, was also an early road that predates any of the existing structures. West and south of Rolling Road are two separate developments. The eastern boundary is Mellor Avenue, which was laid out for residential development just west of the now-vanished Catonsville Short Line railroad tracks and the industrial buildings that bordered the tracks. The neighborhood consists generally of rectangular lots, the largest lots being found on Frederick Road and Newburg Avenue. These contain the earliest dwellings. The district is entirely residential. A large percentage of the district consists of the Summit Park development, with lot sizes that are rather uniform and only slightly smaller than those on Newburg Avenue. The vast majority of these houses are freestanding, single family dwellings. The lots on Mellor Avenue and Sanford Avenue, which were developed separately from Summit Park, tend to be the smallest in the district, and a number contain duplexes that were built concurrently with the single-family homes. The earliest buildings in the neighborhood exhibit the greatest variety in house types and stylistic details. Perhaps the earliest, and the largest, in the district is the Gary Mansion, known as The Summit, built in the 1850s as a summer house in Second Empire style, and listed separately on the National Register. The Summit Park subdivision takes its name from this house, and surrounds it on all sides. Several houses on Frederick Road also date to the summer home period of Catonsville, though not quite as old as The Summit. Two are Gothic Revival frame houses with cross gables on the fronts flanked by smaller dormers. The cross gable form can be found in other early houses in the district, although in a more simplified form. These are located outside the Summit Park neighborhood, in the earlier developments on Newburg, Magruder, and Sanford Avenues. A few Queen Anne examples and some Temple-front houses occur in the district, again outside Summit Park itself. Another style is a frame "ell house", with a front-projecting ell or wing either centered in a "T" plan or to one side in an "L" plan. These invariable have a wraparound porch, with the front door often set back in the main block of the house, adjacent to the ell. Within Summit Park, Bungalows, American Foursquares, Georgian Colonial Revivals, and Dutch Colonial Revivals predominate. There is one example of a Spanish Colonial Revival, a small number of Cape Cod houses, and several ranch houses within the district.
The Central Catonsville and Summit Park Historic District is significant for its architecture, as it embodies the distinctive characteristics of its type and period, illustrating the evolution and development of a community from summer homes to year-round suburban living in the late 19th and early 20th centuries. It is significant both for its community planning, which did not follow the more traditional, and better studied models, and for its architecture, which represents with good integrity the period of its development. Many of the themes, trends, and personalities identified earlier in the development of the Old Catonsville Historic District on the north side of Frederick Road were equally involved in the development of Central Catonsville, which occurred at much the same time on the south side of Frederick Road. The period of significance for the district begins with the initial development of the Central Catonsville and Summit Park area in 1869 and extends to 1958, by which date the neighborhood had substantially achieved its present form and appearance.