Riverdale began as a working-class neighbourhood surrounding the industries associated with the Grand Trunk Railroad, constructed in the 1850s. The land north of Queen Street was annexed by the City of Toronto in 1884, after which development gradually spread north and east. The construction of the Prince Edward Viaduct across the Don Valley in 1918 cemented north Riverdale's connection to the city and accelerated development. Most development occurred between the 1880s and the Great Depression of the 1930s. Incremental redevelopment since the Second World War has not redefined the fine-grained pattern of streets and lots.
Riverdale is extraordinarily dense, both in gross and net terms. Despite its low-rise housing stock -- mostly detached (18%) and semi-detached (34%) two- and three-storey houses on narrow lots -- its net residential density is two or three times that of some postwar suburbs. Only a small proportion of dwellings is in the form of apartments over five storeys; indeed, there are only four large apartment buildings in the entire study area. About 22% of the dwelling stock is in the form of low-rise apartment units. These are distributed throughout the neighbourhood fabric and are perhaps, along with the small lot sizes of the ground-related housing, responsible for the high gross density of the area.
Despite the presence of a large number of jobs, schools, shops, and services mixed into the residential urban fabric, as well as a continuous street grid and high-frequency transit system, most journeys to work and shopping are by automobile.