It's believed the pharaohs of Egypt first used the circle, a shape with no beginning or end, as a symbol of eternity, but wearing a ring as a public pledge to honor the marriage contract did not become customary until Roman times. The earliest rings were made of simple iron, but gold rings set with gems were fashionable by medieval days. The most popular gems were symbolic—a red ruby was the color of the heart, a blue sapphire reflected the heavens—but the most coveted and powerful gem was the indestructible diamond.

Dual-ring ceremonies, in which both bride and groom wear a ring, were introduced by the Greek Orthodox Church in the 1300s.  The custom didn't catch on in America until the beginning of World War II, when young men were forced to leave their beloveds behind, not knowing when and if they would return.  Many couples married in anticipation of separation, and wedding bands—one for each partner—were considered critical to the war effort, as a solace to lonely soldiers and as a reminder for brides that their faraway soldier thought of them always. By the height of the war, 85 percent of marriages were dual-ring ceremonies. And of course, they continue to be today.