When Jennie Jerome and Lord Randolph Churchill announced their engagement in 1874, his parents were horrified. The couple had only known one another for three days, and Jerome—the tattooed daughter of a philandering financier and a social climber—was an American socialite, not a British noblewoman. Appalled, the Churchills tried to block the match…until they did the math.

Jerome’s family might have humble origins, but they were outrageously wealthy. Lord Randolph’s parents were not, and Jerome’s father was willing to pay a dowry that equaled the equivalent of over $4.3 million dollars today. The marriage went forward with the grudging approval of Lord Randolph’s parents.

They could have no way of knowing that Jerome, who became Lady Randolph Churchill when she married in 1874, would be the mother of a future prime minister, Winston—or that by allowing their aristocratic son to barter his title for much-needed wealth, they had helped spark a trend.

Between the late 19th century and World War II, a flood of “dollar princesses” flocked to England looking for love. In return for a coveted title, they offered their much-needed wealth to an aristocracy desperate for cash. And along the way, they helped change British royalty forever—including the lives of the modern-day heirs to Britain’s throne.

Jerome was just one of hundreds of heiresses thought to have injected the equivalent of a billion pounds into the British economy. The exchange was worth it in their eyes; they knew that marriages to people with titles like Lord, Viscount and Duke would improve their family’s fortunes back in the United States and solidify their position on the American social circuit.

The interest was reciprocal. By the late 19th century, the British nobility was down on its luck. Though they owned extensive lands and massive homes, the Gilded Age was tough on the aristocracy. Their lives were financed by their agricultural holdings, but when the United States began cultivating grain on its prairies, England, which had been a worldwide leader in grain production, suffered. As rural populations fell, so did the fortunes of aristocrats.

This depression turned the landed gentry, which had once been the world’s wealthiest, into second-class citizens compared to America’s elite, who were becoming ever wealthier thanks to the United States’ rich natural resources. And since by default, the aristocracy didn’t work, all those newly cash-poor dukes and viscounts sat by as their fortunes fell even further.

Meanwhile, American socialites coveted what they saw as the social status of members of the British aristocracy and royalty. Many of the heiresses of the up-and-coming Gilded Age magnates were daughters of self-made men who didn’t have the social standing of longtime members of high society, and they had trouble gaining acceptance among well-heeled New Yorkers who shunned what they saw as “new money.” A title was seen as a shortcut to social acceptance, and plenty of British aristocrats were willing to trade their titles for cash.

If the marriages sound like cold, hard contractual negotiations, they were. And many of the women who went to England to seek love exchanged their home ties and their comfort for their new titles. Most American heiresses had grown up with modern conveniences. But “after marriage, they found themselves chatelaines of houses where taking a bath involved a housemaid making five trips from the kitchen in the basement, carrying jugs of hot water to fill a hip bath,” author Daisy Goodwin writes in Newsweek. “The stately homes of England were all too often dark, dingy, and terribly cold.”

In response, these new wives began to remodel the homes they now inhabited—and often faced snide judgment for doing so. They also faced dismissal and sometimes full-blown ostracism for their non-aristocratic roots. The aristocracy mocked the “dollar princesses” for their social pretensions and turned up their noses at American culture. But back in the United States, that seemed like a small price to pay for a title and entree into a circle so exclusive, no American woman could ever be born into it.

Their enterprising mothers, who helped broker the matches, weren’t their only allies: There was even a publication called Titled Americans that not only listed women who had snagged aristocratic titles, but still unmarried men, their titles, and their reputed fortunes. Armed with this information and introductions from wealthy friends, American girls descended on London every social season.

They succeeded: In 1895 alone, nine heiresses married European men with noble titles. Notable matches included that of railroad heiress Consuelo Vanderbilt to the Duke of Marlborough and dry goods heiress Mary Leiter to Lord Curzon. “Though the British peerage has of late years yielded many titled husbands to American heiresses,” declared the San Francisco Call in 1904, “there is no danger of the supply running short.”

The trend only slowed once the newly rich women who had been shunned by American high society for so long began to be accepted. Now that the economy was all but controlled by wealthy men who had made their own fortunes, high society could hardly snub them or their daughters.

By then, the idea of the “dollar princess” had become so ubiquitous that it was part of a pop culture trope. And traces of the trend can be found even in the British royal family: In 1880, stock and railway heiress Frances Ellen Work married the future Baron Fermoy. Like many “dollar princess” matches, it was an unhappy one, and the couple divorced in 1891. A mere baron might sound far from the throne, but not really: Just over a century after Work traded her money to the aristocracy, her great-granddaughter Diana became the Princess of Wales.