Apartment City investigates the high-rise apartment boom that took place in post-war Toronto. After 1950, pro-growth politicians and business interests undertook a large-scale program of private rental apartment construction. By the end of the 1960s, an increasingly consolidated development industry had replaced a number of low-rise neighbourhoods with a radically different form of housing: high-rise apartment towers using modernist designs. The apartment boom had a major impact on the city's built form, planning system, housing market, and property rights. Urban planning expert Paul Hess and historical geographer Robert Lewis argue that the apartment boom was the product of an institutional fix that worked to adjust property rights using tools such as zoning, construction finance, and planning oversight. Politicians and developers sought to achieve political and economic value from apartment projects using the twinned narratives of redevelopment and decay. Apartments became the focal point of an active ratepayer politics as residents fought developers looking to build apartments, many in middle-class areas of low-rise houses. Despite this resistance, pro-growth actors successfully redeveloped these neighbourhoods into high-rise apartment districts that became home to young professionals and the elderly.

In the process, Toronto was transformed from a small, parochial city in 1945 to the centre of a vibrant metropolis by the 1970s.