This historic ranch is set to become the world’s most expensive estate after it was put on the market for £460 MILLION. See SWNS story SWRANCH; The W.T. Waggoner Estate Ranch is the largest single ranch in the USA – with a staggering 510,000 acres of land. It is larger than Greater London and spans six counties across Northern Texas. The ranch, which is spread over more than 800 square miles, has 7,500 cows, 500 quarter horses, 20 cowboy camps and numerous huge lakes.