Pennies in the United States were made of pure copper from 1793 to 1837, and then contained varying amounts of copper throughout the years before converting to a majority 97.5 percent zinc in 1982. At that point, the penny continued to be made with a small 2.5 percent copper.
The most common materials replacing or mixing with copper over the decades were bronze, tin, nickel, zinc and zinc-coated steel. In 1943, copper was removed from the penny in order to utilize the metal in the war effort of World War II. A small number of copper pennies were minted that year and have since become valuable collectors items.