If you eat a meal in a Wisconsin restaurant and want margarine instead of butter, you have to ask for it. Wisconsin law forbids the substitution of margarine for butter in a public eating place. A few lawmakers tried to overturn the law in 2011 but failed in their effort. Under the law, students, patients, and inmates in state institutions will be served butter with meals unless a doctor says that margarine is necessary for their health. And when you shop for margarine in a Wisconsin grocery store, you must buy a whole pound colored a certain shade of yellow and labeled in letters of a specific size. And don’t even think about making that margarine with imported oil—only domestic vegetable oil can be used in Wisconsin margarine.

Think everything in the Midwest is canned soup, processed and fake? Think again. And Wisconsin’s oleo-war is the ultimate example.

The “Oleomargarine Regulations,” otherwise known as Wisconsin Statute 97.18, are the last fragments of a once mighty law that shielded Wisconsin citizens from the dangers of butter fakes like margarine. Wisconsin was the last state in the country to permit the sale of margarine colored yellow to look like butter. And that was in 1967—nearly a century after margarine was first produced in the United States.

From the start, the artificiality and industrial origin of margarine, or oleo, as it was then known, inspired fear and suspicion. Its main selling point was its low cost. Farmers, not just in Wisconsin, but across the country saw margarine as a phony, a factory-made good contrary to the superior moral values and virtues of farm-produced products. Not that butter being produced on many of these farms was so wonderful.

So bad was the overall quality of Wisconsin butter at the time, that it was known in the Chicago markets as “western grease” and was sold as a lubricant, not for human consumption. All that began to change after the formation of the Wisconsin Dairyman’s Association in 1872, an organization that quickly recognized that unless butter improved in quality, margarine would drive Wisconsin butter off the market. Wisconsin passed its first anti-margarine law in 1881, the first of many laws that imposed taxes, licenses, and labeling restrictions on manufacturers. The most potent weapon against the demon spread, though, was an 1895 law that prohibited the manufacture and sale of margarine colored yellow in imitation of butter. Grocers and restaurateurs caught trying to palm off margarine for the genuine article faced fines of $50 to $500. Get caught twice and you were sent to jail.

By 1910, margarine manufacturers began to fight back by including packets of coloring for purchasers to tint the naturally pale margarine according to taste. Pro-butter interests continue to argue against colored margarine, claiming that yellow was the natural and unique color of butter and that any shade of yellow margarine was an attempt to deceive the consumer. Colored margarine was banned outright in Wisconsin in 1931—to both buy and to use – though the inclusion of packets of coloring was never outlawed.

Post-World War II conditions favored the repeal of anti-margarine laws, particularly as more and more Wisconsinites began smuggling in yellow margarine from our lax neighbor to the south Illinois because it cost less. The decades long tussle officially came to an end on July 1, 1967, when Governor Warren Knowles signed legislation legalizing colored margarine using a yellow pen and wearing a yellow tie. While eliminating the color restrictions, the remaining restrictions remind us that in Wisconsin, butter once stood for the good, the true, and the pure.