According to The Knot, 70 percent of American women wear that tradtional design. (The practice of wearing it on the fourth finger of the left hand dates back to the Romans, who thought a vein in that finger connected directly with the heart.
The first example of a modern engagement ring dates back to 1477. That year, Holy Roman Emperor Maximilian the First gave Mary of Burgundy a diamond ring as an engagement present. We'd assume she liked it more than a thimble, which used to be a common betrothal gift. (Or a golden nose ring, the first example of a ring given as an engagement present in Judaism.)