Theo Vermaelen’s ironic letter about the idea of purchasing Greenland (“Trump and Greenland: it’s a winner all around,” August 30) was fun, but ended with a serious point: “The current frontiers of countries are mainly the result of wars.” However, the frontiers of the United States were heavily influenced by purchases: the 1803 Louisiana Purchase of 827,000 square miles, the 1854 Gadsden Purchase of 30,000 square miles, and the 1867 Alaska Purchase of 586,000 square miles. In this context, one cannot help noticing similarities between Alaska and Greenland.