In 1948 the Nationalist Party won the general election on a platform of separate development. In 1950 the government passed the Group Areas Act, a cornerstone of Apartheid. The Act divided South African residential areas along racial and ethnic lines designating residential areas for Blacks, Whites, Indians, and Coloureds. This resulted in a many forced removals from areas like District Six and Sophiatown, uprooting millions.
References

Davenport, T. H. (1977). South Africa: A Modern History. Macmillian: Johannesburg.