First Bats

• According to Baseball-Bats.net, the first bats were created in a range of shapes and sizes, including flat ones. Players made the bats themselves and discovered that rounded barrels were most effective. A variety of designs for the handles, knobs and barrels of bats were tested until the 1920s when a more uniform shape took hold. Rounded-barrel, slim-handled bats are common today.
  
  

Louisville Slugger

• Louisville Slugger, the first brand to develop for baseball bats, started in the 1880s and remains prominent today. According to the company's website, the brand began when 17-year-old John Hillerich saw a Louisville player named Pete Browning grow frustrated after breaking a favorite bat. Hillerich, who worked in his family's woodworking shop, offered to make Browning a new bat. Demand grew after Browning found success with the bat, and the Hillerichs added its trademark logo to each bat it made.
  
  

Endorsements and Bats

• Baseball bats were among the first kinds of sporting equipment to carry endorsements from athletes, according to "The Evolution of the Baseball Bat," an article published in Oldtyme Baseball News in 2000. Honus Wagner, the future Hall of Fame shortstop for the Pittsburgh Pirates, signed a contract in 1905 with J.F. Hillerich and Co., the company that produced Louisville Sluggers, that put his autograph on the barrel of a series of bats.
  
  

Size

• Many of the bats used by players in the early 20th century were extremely heavy. For instance, Frank "Home Run" Baker, who led the American League in home runs four times in the early 20th century, used a 52-ounce bat, while contemporary hitters' bats are under 40 ounces. A rule in 1859 limited the size of a bat's diameter to 2.5 inches, which was increased to 2.75 inches in 1895, and the length of a bat was limited by rule to 42 inches in 1869.
  
  

Metal Bats

• The metal baseball bat was invented in 1924 but it was not manufactured widely until Worth introduced an aluminum bat model for sale in 1970, according to "The Evolution of the Baseball Bat." Easton improved the grade of aluminum in its bats in the late 1970s, starting an increase in popularity of the bats, which send the ball further than wood bats. Professional leagues have never allowed non-wood bats for competitive and safety reasons.
  
  

Types of wood

• The wood used most often in bats over the years has been white ash. Hickory was used in the first bats of the mid-1800s, according to Baseball-Bats.net, and then wagon tongue became popular. Maple wood bats began to grow in popularity in the early 21st century, especially after Barry Bonds hit 73 home runs with maple wood bats in the 2001 season. The bats have proved controversial because of the explosive way that they shatter.