The era of sand and antelopes vanished completely in little more than a generation. Vegetable farming persisted, but to a much lesser extent, because urbanisation enveloped vast tracts of land in short order. During the apartheid era, race-based legislation such as the Group Areas Act and pass laws either forced non-white people out of more central urban areas designated for white people and into government-built townships in the Cape Flats, or made living in the area illegal, forcing many people into informal settlements elsewhere in the Cape Flats. Large housing projects were built here, mostly as part of the Nationalist government's larger effort to force the so-called Coloured community out of the central and western areas of Cape Town, which were designated as white areas under the Group Areas Act. This meant that only whites could reside there permanently; as under the apartheid system black Africans were officially citizens of the independent homelands, regarded as temporary migrant workers, therefore having resident worker status. However, since many of the mostly Xhosa initial migrant workers bore children, these children who were born and raised in the Cape Town area—were designated under apartheid as residents of Bantustans, many were obliged to live in the area illegally, further contributing to the growth of informal settlements. Apartheid did not anticipate the eventuality of black migrant workers not returning to their homelands, effectively not permitting naturalization. Additionally, other large townships of black people (such as Khayelitsha and Gugulethu) grew up on the flats as a product of mostly informal settlement, but also forced government relocations to a lesser extent. These consisted in the main of shacks made of "tin" (in reality corrugated iron which, confusingly, is nowadays made from mild steel), cardboard and wood. In 1993, Cape Town had a housing backlog of approximately 40 000 houses and with the numbers of people migrating from the rural areas increasing each year, so the backlog increases. One of the major priorities of the RDP (Reconstruction & Development Programme) is to build houses.