Prior to the onset of the Second Boer War, Kimberley was the second-biggest city in the Cape Colony, and vibrant and prosperous as the centre of diamond mining operations of the De Beers Mining Company, who supplied 90% of the world's diamonds. The town had a population of 40,000, of which 25,000 were white. It was one of a handful of British outposts in the far north east of the colony, located just a few kilometres from the borders of the Boer republics of the Transvaal and Orange Free State; Cape Town was away by rail, while Port Elizabeth was . The closest Boer settlements were Jacobsdal to the south and Boshof to the east.