Salad is hardly new. According to historians, ancient Greeks and Romans had oil-based dressing on raw vegetable. The poet Virgil describes a rustic salad made of herbs, vinegar, and cheese. Oregano-flavored olive oil—suspected to be for salad dressing—was discovered in a 2,400 year old shipwreck in the Aegean Sea. But despite its ancient roots, America’s salad sector wasn’t always so vibrant.