The foundations of Apartheid in South Africa. Social engineering on a grand scale. This involved:

The population registration act of 1950 decreed that everyone had to be categorised as one of White, Black, or Coloured, (i.e. Asian, Indian, or of mixed descent.)

The creation of homelands or bantustans recognised only by South Africa, so that many black people found themselves to not actually be citizens of South Africa, just visitors needing papers not to be deported.

The Group areas act of 1950, urban planning creating segregated cities.

See also Petty Apartheid