He isn't the first to suggest US acquiring Greenland.
Since 1867, the United States has considered, or made, several proposals to purchase the island of Greenland from Denmark, as it did with the Danish West Indies in 1917. While Greenland remains an autonomous territory within the Kingdom of Denmark, a 1951 treaty gives the United States much control over an island it once partially claimed from exploration.
Yeah I recall him saying maybe we should buy Greenland from Denmark.
Media blasted him as a “stupid idea”. But it put spot light on Greenland and arctic issues
He isn't the first to suggest US acquiring Greenland.
https://en.wikipedia.org/wiki/Proposals_for_the_United_States_to_purchase_Greenland