Perhaps the one single experience which North American cities have in common is the decline of the central business district. The Downtown of the North American city is undergoing a profound change in the nature, extent, and intensity of its traditional activities. The flight of population, wholesaling, warehousing, and manufacturing from the Downtown has been going on for four or five decades, and is thoroughly documented in thousands of scholarly treatises, newspaper reports, in the annual reports of the business corporations of North America, and indeed in the Report of the Greater Winnipeg Investigating Commission of 1959. More recently there has been a flight of what has always been thought to be the true heart of the downtown business activity retailing, and to some extent commercial offices, hotels, entertainment, and high-rise apartments.

At the same time certain traditional Downtown activities have not moved out but have remained Downtown, and, if anything, have strengthened their position, so that the Downtown is emerging as the area of specialization in such things as service employment, government, financial institutions, and to some extent of entertainment and of quality retail goods.

The changes which have been taking place in the structure of the city are due to a number of complex forces. The changes in the location of wholesaling and warehousing, for example, have followed from fundamental changes in the organization, and in the technology of these industries. Closer integration with retailing, the use of the mechanical fork lift, the greater operational efficiency of horizontal rather than vertical building space have all been important pressures forcing these activities out of the central area. to these may be added, in some measure, the difficulties in finding room to expand in the Downtown, and the difficulties of transportation and access, because of traffic congestion, particularly in the very large cities. Much the same observations may be made of the manufacturing industries. Many manufacturing industries during and after the war underwent very extensive reorganization and re-equipping, and found that they could only do so on new sites which were only available in suburban locations. These various pressures have succeeded in forcing relocations in many instances in spite of the fact that a central area location might be an advantage from the point of view of distribution of the product.

As for housing, the exodus of the middle classes to the suburbs has been going on ever since the almost universal adoption of the private automobile as the principle mode of urban transportation. The widespread use of the private motorcar has permitted a flood of population out of the central city into the surrounding countryside; and the exodus has drained the Downtown of its resident population, and much of its potential new retail investment.

The effects on the Downtown of the flight from the central city have been to leave behind as the residual resident population the poor and the aged of the city; to leave a high proportion of floor space either vacant or occupied at very low rentals by, in many cases, marginal tenants; to leave large site areas either vacant or used as surface parking lots; to create serious over-congestion on the Downtown streets and on the major arteries between the residential suburbs and the Downtown employment centre, particularly at peak hours; and to spread a general air of deterioration and neglect, even of abandonment, over the entire central business district.