From the formation of the Union in 1910, the South African state viewed immigration policy as an essential part of building, and protecting, the nation. The 1913 Immigrants Regulation Act, by excluding ‘non-white’ immigrants established that the South African state saw the territorial entity of South Africa as an exclusively white nation, despite the millions of Africans, Indians and coloured people within its boundaries. In the 1920s and 1930s, as South Africa started its post-war nation-building process, it emerged that the definition of whiteness and white national identity was both flexible and contested. Jewish immigrants were excluded because a secondary qualification for national membership was invented. New members of the nation had to be white, but they also had to be related to, or from, the fictive ‘original stocks’ of the country, the British and Afrikaner. To limit the entry of those who were seen to have the potential to contaminate the stocks of the nation, the state introduced the Aliens Act in 1937. In so doing, it created a two-tier immigration system that privileged British immigrants who only had to meet the terms of the 1913 Immigrants Regulation Act, while immigrants from all other countries had to comply with both the 1913 and 1937 Acts.