South African cities were highly segregated in the twentieth century as a result of the attempt by the White minority to maintain political and economic dominance. Until the 1950s there was no systematic plan for achieving these objectives. Colonial segregation practices were tightened after the establishment of a united South Africa in 1910, but only in 1948 did official policy involve the broad replanning of the cities with the goal of achieving total segregation—apartheid. By the 1980s these began to be modified in detail, although remaining legally in place until 1991. The last ten years of the century involved a rearguard attempt to preserve the position built up earlier in the century. Segregation was imposed upon defined population groups differentially, through a mass of legislation and regulations. Thus, Africans were tightly controlled throughout the century, whereas control over the Asian and Coloured populations was less restrictive before 1950 and again after 1984. The result was a constant flux in the level of segregation. Successive censuses offer an insight into the changes effected in the South African city in the twentieth century.