Margarine was invented in 1869 as a butter substitute. Because the animal fats used in its production at the time were primarily meat byproducts, margarine was a much cheaper alternative to pure butter. The creamy spread threatened the profit margins of U.S. dairy farmers. In 1886, farmers sent petitions to Representative William Fuller of Iowa, requesting that “ALL imitations of Butter and Cheese, manufactured or sold in the United States, or used on the tables of public eating houses” be identified with a stamp. Although petitions in the House records included many signatures on a single document, each of these petitions was an individual postcard, signed and mailed by a single citizen.
On July 23, 1886, Congress passed the Oleomargarine Act, which imposed a tax on the butter substitute. Stamps were used on the packaging to indicate that the tax had been paid. After margarine producers started using more ingredients grown on farms, rather than animal fat byproducts, support for the tax waned. The law was repealed in 1950.