Denmark turned down 100m USD from the USA in 1946; I discuss how this was a bad idea—America got what it needed anyway while Denmark kept control of a loser.
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After WWII, the Cold War motivated the USA to offer $1,286.3$1001946 million for ownership of Greenland, which was declined. The USA got the benefit of using Greenland anyway.
I discuss how the island otherwise remained a drain since, the dim prospect it will ever be useful to Denmark, and the forgone benefits of that offer.
Following World War II, the United States developed a geopolitical interest in Greenland, and in 194678ya the United States offered to buy Greenland from Denmark for $1,286,300,994.03$100,000,0001946 , but Denmark refused to sell.
The reason why the US would want to buy Greenland is clear: being able to install anti-Russian military installations such as early-warning radar and nuclear bomber bases (Greenland being fairly close, on a great circle, to Russia)1. The US has famously often bought large chunks of land (Louisiana Territory & Alaska being the biggest & most profitable), so it was nothing new—this was, in fact, the second time the US expressed interest in buying Greenland, after an abortive attempt in the 1860s. It would not even have been the first sale of Danish land to the USA, as there was at least one other, the United States Virgin Islands in the Treaty of the Danish West Indies. (As should be no surprise: transfers of land are an important way that geopolitics can be improved without requiring war.)