During World War II, consumer goods were restricted so that materials could be used for the military. This included food staples like sugar and butter, and most metals. It also applied to shoes. From February 1943 to October 1945, Americans could only buy three pairs of shoes per year.
Shoes were rationed because leather and rubber were in short supply. (Rubber especially, as Japan controlled Southeast Asia, where the bulk of the world’s rubber was produced.) Hoping to avoid serious shortages, the OPA set a cap on shoe purchases, and issued new rules about the kinds of shoes that manufacturers could make. Only four colors were permitted — “black, white, town brown, and army russet” — and two-toned shoes were prohibited. Further disappointing the nation’s snazzy dressers, the OPA banned boots taller than 10 inches, heels taller than two-and-five-eighths-inches, and “fancy tongues, non-functional trimmings, extra stitching, leather bows, etc.” The resort set felt the pinch, too: men’s sandals and golf spikes were deemed inessential, and discontinued.
There were some exceptions. If you lost your shoes in a flood or fire, or if they were stolen, you could, mercifully, apply for a special certificate to buy a new pair. Mail carriers, police officers, and others whose work was hard on their feet were also exempt. Allowances were made for orthopedic and maternity shoes and a few other cases. Otherwise, the three-pair limit stood firm, but the OPA figured it was better than the alternative: compelling manufacturers “to produce shoes that would be so unattractive that people would not buy them unless absolutely needed.”
It's hard to believe that any adult would ever need more than three new pairs of shoes per year, but maybe they didn't last very long in the 1940s. You can read more about the shoe rationing program and see lots of pictures from that era at Smithsonian.