In 1915, this man, Charles Willes, was convicted of breaking the Oleomargarine Act. He was sent to the Federal Penitentiary at Leavenworth for being guilty of “crimes against butter.” As the National Archives explains, the problem was margarine:
How did trafficking in this popular butter substitute become a Federal offense? Well, almost immediately after New York’s U.S. Dairy Company began production of “artificial butter” in 1871, regulation began. Dairy interests pushed Congress to pass the 1886 act, which imposed a two-cent tax (per pound) on margarine and also required manufacturers, wholesalers, and retailers of margarine to obtain margarine licenses.
By 1902, 32 states had bans on coloring margarine yellow to make it look more like butter. That same year, Congress increased the tax to 10 cents a pound for colored margarine but imposed a lesser tax of a quarter of one cent per pound on the uncolored stuff … Some tried to pass the margarine off as butter; others tried to evade the tax by reusing tax stamps again and again.
Consumers colored their own margarine with yellow food coloring into the 1940s. The federal margarine tax system came to an end in 1951. In 1967, dairy state Wisconsin was the last state to repeal the restrictions on the sale, coloration, and/or manufacture of margarine.