I remember my grandfather taking me to lunch at a cafeteria in Jackson, Missouri, sometime in the 1950s. They had margarine, but it could only be served in little pats, cut in triangular shapes, to distinguish it from real butter. It was one of many laws written to protect dairy interests, and I bet it's still on the books. When I was in the service, military messes and chow halls could only serve real butter. Don't know if that's still the case.