>> it's located 750 miles north of the arctic circle which remains a critical area of the globe in terms of our ability to thwart and defend against particularly russian threats. >> reporter: and history suggests this truly may not be a crazy idea. in 1867, the u.s. bought another huge cold place which was mocked as a folly. but alaska has worked out pretty well for american interests. and two times before u.s. officials have raised the notion of buying greenland. still, the outlook for this real estate deal is not promising. "it's not something you buy or sell. if countries want other territories, it's war." next month president trump will travel to denmark to meet with the prime minister and the premier of greenland. whether he will take his checkbook, no one knows. tom foreman, cnn, washington. joining us now, contributor and trump biographer michael d'antonio, author of the book