Lariats are an American jewelry invention. A lariat is a long, usually single strand necklace, that does not have a clasp. Initially popular in the late 1800's during the Art Nouveau Period, they reached their zenith during the Roaring 20s. Initially, lariats were only a few feet long, but true to the American belief that anything worth doing is worth overdoing, they got longer and longer. Zelda Fitzgerald had a pearl lariat that was one hundred feet long.
Such extremely long (and expensive!) lariats went out of fashion during the Great Depression. Nowadays it's considered ideal if the length of the lariat equals the height of the wearer, because that is the perfect length to wear in a variety of ways, around the neck as well as around the waist. A most alluring look with backless gowns and cocktail dresses.