Between the 9th and 15th century, open trade allowed a number of cities in Italy to obtain independence from their formal sovereigns. Today there are only a handful of city states - Singapore, the Vatican, and Monaco. There are a number of small countries where the definition blurs. Monaco has a total area of 2.02 km^2 and a land border of 5.47km. It started it's current life as a colony of Genoese (Italian) city state. In 1419, the Grimaldi family purchased Monaco, formalising their claim, from the Crown of Aragon. They are now a constitutional monarchy, and have ruled the area (with interruption) since 1297. At times under attack, it became a vassal of the French Monarchy, up to the French Revolution. Its defence is still the responsibility of France. In 2014, 30% of its population were millionaires. Monaco became a full voting member of the United Nations in 1993.