The baseball bat is an evolution in and of itself. First making its debut in the 1850s, players could play with any bat without any size or weight restrictions. As the sport took off though, limitations were put on the bat to ensure that all players had equal opportunities. In 1859 The Professional National Association of Baseball Players first voted that a bat that was 2.5 inches in diameter was sufficient in width, but no length restrictions were placed on the bats as of yet. As time progressed, the association voted that a bat should be no more that 42 inches in length. Although this rule was created in 1869, the rules and regulations for baseball bats have not changed and the 42 inch length is still a required regulation.
Although wooden bats seem to be the most common types to use, the aluminum bat made its debut when patented in 1924. Due to the significant change in material, aluminum bats were not used professionally until the 1970s. Although the aluminum bat gained popularity, the association has never allowed them to be used in Major League Baseball for safety and durability reasons. It is very common to still see a wooden bat used in action that was played with more than a century ago.