In 1917, Johannesburg became the headquarters of the Anglo-American Corporation founded by Ernest Oppenheimer which ultimately became one of the world's largest corporations, dominating both gold-mining and diamond-mining in South Africa. Major building developments took place in the 1930s, after South Africa went off the gold standard.[citation needed] In the late 1940s and early 1950s, Hillbrow went high-rise. In the 1950s and early 1960s, the apartheid government constructed the massive agglomeration of townships that became known as Soweto. New freeways encouraged massive suburban sprawl to the north of the city.[citation needed] In the late 1960s and early 1970s, tower blocks (including the Carlton Centre and the Southern Life Centre) filled the skyline of the central business district.