Stiffel Company (Stiffel) (plaintiff) designed and manufactured a pole lamp, which was a type of floor lamp with external lighting fixtures. Stiffel was issued mechanical and design patents for the pole lamp, which became a commercially successful product for Stiffel. Sears, Roebuck & Company (Sears) started selling a nearly identical version of the lamp at a lower cost, and Stiffel brought a suit against Sears for patent infringement. The district court found the pole-lamp patents invalid for lack of novelty, but nevertheless found Sears guilty of unfair competition and enjoined Sears from selling substantially similar lamps. The court of appeals affirmed the decision, finding that the design of the lamps was identical and likely to cause customer confusion. The United States Supreme Court granted certiorari to determine whether Illinois’s unfair-competition law conflicted with federal patent law.