White Castle is widely recognized as the oldest continuously operating fast-food hamburger chain in the world, having opened its doors in Wichita, Kansas, in 1921. Founded by Billy Ingram and Walter Anderson, the pioneering enterprise revolutionized the restaurant industry by introducing standardized kitchen procedures, pristine stainless-steel buildings to build public trust, and the iconic square-patty slider, laying the foundational blueprint for modern fast-food operations globally.