The map of the United States took shape over more than a century, through a series of purchases and treaties with European powers and Mexico. 

The land itself, of course, had been home to Indigenous peoples for thousands of years before any of those transactions took place.

The opening move came in 1803. For $15 million, the United States completed the Louisiana Purchase, acquiring roughly 828,000 square miles from France, a vast swath of land stretching from the Mississippi River west to the Rocky Mountains and from the Gulf of Mexico north to the Canadian border. That works out to about three cents an acre. Napoleon, who needed cash more than he needed North America, probably regretted it later.

Florida followed in 1819, acquired from Spain for the assumption of $5 million in debts owed to American citizens, about 11 cents an acre. Anyone who has priced waterfront property in Miami recently will appreciate the deal.

Then, after the Mexican-American War, the U.S. paid Mexico $15 million for 338 million acres in 1848: what is now California, Nevada, Utah, and parts of seven other states. About four cents an acre. 

Gold was discovered in California the same year the treaty was signed. The United States may not have known exactly what it was buying, but history rewarded the timing generously. 

Five years later it went back for more: a strip of land along the southern border, purchased for $10 million in 1853 at 53 cents an acre, to secure a route for a southern transcontinental railroad.

Then came Alaska. In 1867, Secretary of State William Seward paid Russia $7.2 million for nearly 600,000 square miles of northern territory, at roughly 2 cents an acre. The press called it Seward’s Folly. Then they found the fish. Then the timber. Then, in 1968, one of the largest oil fields ever discovered in North America. The bargain story has a footnote: Alaska remains one of the most federally subsidized states in the country. But its strategic value, sitting between Russia and the Pacific, has never been in doubt.

The last major purchase was the Virgin Islands in 1917, bought from Denmark for $25 million in gold coins, at $295 per acre. At the time, critics called it an exorbitant sum for a territory barely a tenth the size of Rhode Island. The price was not for the scenery. The islands commanded the sea routes to the Panama Canal, and with a world war underway, the United States was not about to let them fall into other hands.