Mary of Burgundy was probably the first woman to ever receive a diamond ring as a love token upon her engagement to the Archduke Maximilian of Austria in 1477. Her ring, which was made of gold with diamonds that form the letter M, began a trend for the next century, when royals and other nobility chose to show their fidelity with these stones.
Yet, well into the 20th century, diamond rings were still uncommon when it came to marriage proposals. The custom of engagement rings came to the U.S. around the 1840s, but it was only in the 1870s, after the discovery of large diamond veins in South Africa, that diamonds became more available, even to the middle classes.
In 1888, in order to curb supply and control prices in the market, South African miners formed the De Beers Consolidated Mines Ltd. (now De Beers) cartel to protect their investment and profits. De Beers controlled every aspect of the industry — including marketing — investing great effort in convincing the masses that diamonds were rare and a symbol of status. But it would take another half century to make people associate them with love and marriage. Before World War I, most brides appreciated gemstones in their rings, but only 10 percent of these were diamonds.
With the onset of the Great Depression in the 1930s, the diamond trade went into a crisis. The price of diamonds fell globally, as people cut back on luxury and stuck to the basics. Marriage rates also fell, and the couples who did get engaged chose to express their commitment in cheaper rings with small and low-quality diamonds.
With a stockpile to sell, De Beers set on a mission to convince the world of the necessity of diamonds. In 1938, they hired the New York-based ad agency N. W. Ayer, who began a long, concerted campaign to equate diamonds with marriage and commitment.
Using Hollywood celebrities who showcased their diamonds on and off the screen, the campaign sought not to promote a specific brand, but to sell the idea that diamonds, and only diamonds, should be the measure of a man’s love: the bigger and more expensive the rock, the bigger a man’s commitment and the value of the marriage was.