On March 16 President Truman signed legislation to eliminate the ten-cents-a-pound federal tax on yellow margarine, putting the synthetic spread on an equal footing with butter for the first time in sixty-four years. The repeal ended one of the nation’s most glaring examples of a fair trade regulation degenerating into simple protectionism. The controversy dated back to the 1870s, when margarine was introduced in America. At that time it had an unsavory reputation because of its manufacturing method, which was fairly innocuous by the standards of meatpacking plants but sounded unwholesome in more delicate surroundings.

The original process, devised by the Frenchman Hippolyte MËge-MouriËs and patented in 1869, was a not very sophisticated attempt to duplicate a cow’s internal metabolism. Beef suet, finely minced or crushed between rollers, was heated with water, potassium carbonate, and chopped bits of sheep’s stomach. Digestive enzymes from the sheep’s stomach separated the fat from the cellular tissue. The extracted fat was bleached with acid, further digested with bicarbonate of soda and sliced udders, and then blended with milk, water, and a coloring agent. After the solids settled out, a substance resembling butter was left.

Although producers soon found they could do without stomach and udder tissue, the stench of the slaughterhouse remained. The dairy industry heaped abuse on its upstart competitor, calling margarine “a compound of diseased hogs and dead dogs” made from “the raw fats and stomachs of diseased animals, and of those that die on the cars.” A Vermont congressman sneered at margarine as “an alleged article of food” that was “a step back toward the raw tallow and lard which were the delight of our Saxon ancestors in the forests of Germany.” He said it often contained soap grease and the residue of hog slops and called its dubious composition “the mystery of mysteries—a far profounder mystery than hash or sausages.”

Since grocers dispensed butter (and most other goods) from bulk containers, it was easy for an unscrupulous operator to pass off margarine as the genuine article. To prevent this, starting in 1886, a series of federal laws placed heavy taxes and license fees on margarine and restricted its sale with yellow coloring added. Some state laws went much further: A few even required margarine to be dyed pink, red, or black until the Supreme Court struck them down.

Attitudes toward margarine changed as the product itself changed. In the 1880s manufacturers began adding vegetable oils to increase spreadability, and during World War I all-vegetable margarines were introduced. The key advances were improved refining methods, which removed unwanted flavors, and hydrogenation, in which hydrogen is added directly to vegetable oils to make them harder.

With its ingredients and manufacture far removed from the abattoir, opponents could no longer call margarine “slag of the butcher shop.” At the same time, the retail revolution let consumers buy individually labeled packages, greatly reducing the possibility of fraud. Where yellow