The oldest living US dollar billionaire is John Simplot (USA, b.4 January 1909), who had a net worth valued at $3.2 billion (£1.6 billion) when listed on Forbes.com on 8 March 2007, aged 98 years 63 days.
Mr Simplot of Boise, Idaho, USA, self-made his fortune in the agricultural business, most notably in potato products.