During his presidency, Donald Trump's reported attempt to buy Greenland was widely ridiculed. However, his proposal wasn't as outlandish as you might think.

Many countries, particularly the US, have purchased sovereign territory over the years. In fact, in 1916, when America bought the Caribbean islands that we now know as the US Virgin Islands from Denmark, the US actually agreed that Greenland would fall within the Kingdom of Denmark as part of the deal.

Read on for 31 astonishing examples of nations buying all or parts of other nations throughout history. All dollar amounts in US dollars.

Countries have been buying up sovereign territory since the medieval period. Sometime between 1097 and 1101 the Viscount of Bourges Odo Arpinus sold Bourges and Dun in what is now central France to the King of France for 60,000 pounds or shillings.

Historians have suggested the viscount offloaded the territory either to fund a Holy Land crusade or because he had no children to bequeath it to.

Eager to expand Scotland's territory and end the nation's conflict with Norway, King Alexander III paid King Magnus IV 4,000 merks (a long-obsolete Scottish coin) plus an annuity of 100 merks to gain sovereignty over the Firth of Clyde and Kintyre, as well the Hebrides islands and the Isle of Man. The deal was formalised by the Treaty of Perth, which was signed on 2 July 1266.

The Dauphiné de Viennois, an ancient feudal state in modern-day southeastern France, was acquired by King Philip VI of France in 1349 from the heavily indebted and heirless Humbert II of Viennois, who received a lump sum of 300,000 guilders and a generous pension in return. As a result of the purchase, the heir to the French throne was thereafter known as the Dauphin ('Dolphin').

In 1417, the ruler of the Burgraviate of Nuremberg, an affluent territory in what's now Bavaria, Germany, parted with 400,000 Hungarian gold guilders to acquire the Margraviate of Brandenburg, located in modern-day northeastern Germany. The purchase paved the way for the formation of the Kingdom of Prussia. The picture shows a model of the Margraviate capital, Berlin, in 1480.

Russia bagged Estonia, Livonia, Ingria and southeast Finland in 1721 as part of the Treaty of Nystad, which ended the Great Northern War that had raged since 1700. Tsar Peter the Great paid King Frederick I of Sweden two million silver rubles for the territories and handed over most of Finland to boot. The signing of the treaty is depicted in this etching by Peter Schenk the Younger.

Now part of the US Virgin Islands, which features later in our round-up, the Caribbean island of Saint Croix was purchased from France in 1733 by the Danish West India Company, which was acting on behalf of the state of Denmark-Norway. The company paid a total of 750,000 livres for the territory.

After the people of Corsica rebelled during the 1750s against Genoa, which had ruled the Mediterranean island since 1284, the Genoese enlisted the military assistance of the French. The revolt was quelled and Genoa was issued with a hefty bill that it couldn't pay. King Louis XV arranged the acquisition of Corsica in 1768 in lieu of the debt and it duly became a territory of France.

In 1803, the US made the first of many territorial acquisitions when the burgeoning country bought 820,000 square miles of territory from France for a bargain $15 million, the equivalent of around $408 million (£324m) in today's money. The land that made up the purchase covers a vast swathe of modern-day America, including Louisiana, Arkansas, Kansas, Nebraska, and Montana.

The US government got its chequebook out again in 1819 with the purchase of Florida from Spain. Secured in the Adams–Onís Treaty, the territory encompasses present-day Florida and southern parts of Alabama, Mississippi, and Louisiana. All in all, the purchase cost the US $5 million, which works out at around $121 million (£96m) in today's money.

Singapore became a de facto British possession in 1819 when Stamford Raffles (pictured) signed a treaty with the Temenggong Abdu’r Rahman and the Sultan of Johor to purchase the territory for the British East India Company. The Sultan received an annuity of 5,000 Spanish dollars, while the Temenggong was awarded a yearly payment of 3,000 Spanish dollars.

Having successfully bagged the Louisiana Territory and Florida, the US government negotiated with local Native American tribes in 1836 to acquire 3,149 square miles of land in the modern-day northwest corner of Missouri. The Platte Purchase, as it was named at the time, cost just $7,500, a paltry $248,000 (£197k) when adjusted for inflation.

As the British government tightened its grip on India, the powers that be bought Frederiksnagore (modern-day Serampore) in 1839 from Denmark and followed up the purchase with the acquisition of the fortified Danish outpost of Dansborg (Tranquebar today) in 1845. The cash paid amounted to £125,000, which translates to £17 million ($22m) in 2023.

In 1848, the US government signed the Treaty of Guadalupe Hidalgo with Mexico, ending the Mexican-American War. As outlined in the treaty, the US agreed to pay Mexico $15 million – the equivalent of $584 million (£464m) today – and settle the claims of American citizens against Mexico in exchange for 525,000 square miles of land spanning modern-day Arizona, California, Nevada, and Utah.

Mexico sold yet more territory to the USA in 1853 in what became known as the Gadsden Purchase, named after James Gadsden (pictured), the US ambassador to Mexico at the time. In desperate need of hard cash, the Mexican government relinquished 29,670 square miles of territory in what is now Arizona and southwestern New Mexico for $10 million. In today's money, that works out to around $400 million (£318m).

As part of the Gastein Convention, a treaty signed by Austria and Prussia in 1865, Austria sold the territory of Saxe-Lauenburg in present-day northern Germany to Prussia for 2.5 million Danish rigsdalers. However, Austria didn't hold on to the territory for long, losing the land a year later following the nation's expulsion from the German Confederation. The freezing out of Austria was orchestrated by Prussian statesman Otto von Bismarck (pictured), who became Germany's first Chancellor.

Back to the US. After a period of negotiation with Russian diplomat Eduard de Stoeckl, US Secretary of State William Seward secured the purchase of Alaska in 1867 for $7.2 million, around $150 million (£119m) in 2023 money. Initially derided by some as 'Seward's Folly', the acquisition paid off handsomely when huge quantities of gold were discovered in the Last Frontier in 1896, sparking the Klondike Gold Rush.

Pictured here is the actual cheque used to pay for the territory.

The Dominion of Canada got in on the action with the purchase of Rupert's Land, which included modern-day Manitoba, the lion's share of Saskatchewan, southern Alberta, southern Nunavut and northern parts of Ontario and Quebec, as well as the Northwest Territories. The vendor was the Hudson's Bay Company. The sale was finalised in 1870 and cost the nation £300,000, a figure that translates to just £42 million ($53m) in today's money.

Exasperated with the cost of administering Saint-Barthélemy, the Swedish King Oscar II sold the Caribbean island, which is now a luxury tourist destination, to the French in 1878. In total, the purchase set the French government back 400,000 francs, which, based on the price of gold at the time is around $6.3 million (£5m) today.

Not a purchase as such, the British government negotiated a 99-year lease of Hong Kong in 1898. The contract was signed in Beijing (known as Peking at the time) by China's Li Hongzhang and British diplomat Claude MacDonald, who was convinced the UK would never have to hand back the territory.

Proving the British official wrong, Hong Kong reverted to Chinese sovereignty in 1997. A replica of the lease agreement is pictured here.

The US absorbed even more territory in 1898 following the Spanish-American War. Emerging victorious from the short-lived conflict, America was ceded Guam and Puerto Rico by Spain, granted temporary control of Cuba and gained the Philippines in exchange for $20 million, the equivalent of $741 million (£588m) today.

The transfers were formalised in the Treaty of Paris, signed on 10 December 1898. However, the Philippines did not recognise this deal, which led to the Philippine-American War. America won, but in 1935 the nation was granted commonwealth status. After a brief period of Japanese occupation during World War II, the US gave the Philippines independence in 1946.

A year after giving up sovereignty of Cuba, Guam, Puerto Rico, and the Philippines, the government of Spain came to the realisation it could no longer defend and administer its territories in the Pacific. As a consequence, these islands were sold to the German government for 25 million pesetas, which is around $106 million (£84m) in 2023 money.

This image shows the official transfer ceremony.

A number of Filipino islands were left out of the Treaty of Paris due to an administrative blunder and remained under the sovereignty of Spain. The discrepancy was addressed by the signing of a new treaty in 1900, and the territories were sold to the USA for $100,000, which works out at around $3.7 million (£2.9m) in today's money.

America's temporary control of Cuba came to an end in 1902. The following year, the USA took out a lease on Guantanamo Bay, renting the territory in perpetuity for an annual payment of $2,000 in gold, which works out at around $68,000 (£54k) today, though the amount was raised to $4,085 in 1974.

These days Guantanamo Bay is best-known for being the site of the notorious detention camp of the same name.

In 1903, the newly independent nation of Panama and America signed the Hay-Bunau-Varilla Treaty. It granted the US government a perpetual lease on the Panama Canal and the surrounding land in exchange for a payment of $10 million and an annual rent of $250,000, which is $349 million (£277m) and $8.7 million (£7m) in today's money respectively.

In the end, the US agreed to terminate the lease and the territory was handed back to Panama in 1999.

During the 1880s, Belgium's King Leopold II, along with a syndicate of investors, gained control of the Congo from tribal rulers. He went on to rule his African colony with unimaginable brutality, enslaving much of the population who were forced to work on the territory's numerous rubber plantations.

International pressure eventually forced the merciless monarch to give up the colony, and it was sold to the Belgian government in 1908 for the equivalent of $75 million (£60m) in today's money.

The most recent of America's territorial purchases, the Danish West Indies, was acquired in 1916 for $25 million in gold, which is $708 million ($562m) today when adjusted for inflation. The territory, which consists of three Caribbean islands, was renamed the US Virgin Islands.

Interestingly, the US agreed to recognise Denmark's sovereignty of Greenland as part of the deal, something then-president Donald Trump may not have been aware of. 

This territory, consisting of 69 square miles in modern-day northwestern Russia near the Finnish and Norwegian borders, was sold to the Soviet Union in 1947 for 700 million Finnish marks, which is $58 million (£46m) in today's money. The land was sold so the Soviets could rebuild a hydroelectric plant that would benefit both nations.

Gwadar was an overseas territory of Muscat and Oman for 200 years. A small enclave, the port city was surrounded by Pakistan.

In 1958, the government of Muscat and Oman agreed to sell the territory to Pakistan for $3 million, $32 million (£25m) in today's money, following pressure from the local inhabitants and Pakistani government.

The Netherlands annexed just under 27 square miles of German territory in 1949 as compensation for damage inflicted on the country during World War II. The land, which included the villages of Elten and Suderwick, remained under Dutch control until 1963, when West Germany shelled out 280 million marks, $671 million (£533m) in 2023 money, to get it back.

The Japanese government acted in 2012 to exert its sovereignty over the Senkaku Islands, which are claimed by China and Taiwan, by buying the uninhabited territory from the Kurihara family for 2.1 billion yen, which works out to $28 million (£23m) in 2023 money.

As you can imagine, the deal didn't go down at all well with the governments of China and Taiwan and triggered demonstrations in both countries.

The Republic of Kiribati, a sovereign state in Micronesia in the central Pacific Ocean, bought land on the island of Vanua Levu from Fiji in 2014. The land was purchased as a potential refuge for the Kiribati people when the Pacific islands they currently live on become submerged as a result of climate change.

Kiribati's president, Anote Tong, bought 20 square km of land on Vanua Levu, which lies 2,000km away, for the equivalent of $11 million, (£9m) in today's money.

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