Richard Hellmann, owner of a deli in New York City, decided in 1912 to begin packing his wife’s mayonnaise in individual glass jars instead of ladling out portions and selling it by weight. By 1927, he gave up the deli business to concentrate on manufacturing his emulsion. Thus, the ubiquitous potato salad was born. Photo: “The Food Chronology,” James Trager, 1995, Henry Holt and Co.