Culinary historians and fast-food researchers recognize the hamburger created and sold by White Castle in the United States as the oldest continuously serving hamburger concept in the world. Founded by Billy Ingram and Walter Anderson in Wichita, Kansas, the enterprise began selling small, square-pattied hamburgers in 1916 before formally incorporating in 1921. White Castle revolutionized the global culinary landscape by introducing standardized kitchen sanitation, high-volume mass production, affordable pricing, and a multi-unit supply chain model that successfully established the foundational blueprint for the modern international fast-food industry.