The Dead Ball Era essentially began with the invention of baseball, though some argue that the period truly began in 1900. It was so called because of the distinct lack of offense, low batting averages and a dearth of home runs. Though other factors played a part, the most glaring cause of these trends was the ball itself. The rules governing the manufacture of baseballs stated that the balls had to be wound tight, but they never specified how tight. Stitching processes being somewhat inferior, the balls tended to have a looser covering. At that time, the same ball was used the entire game, making the cover even looser as the game went on. Even if a ball flew into the stands, ushers would retrieve it and it would be used for the next pitch. Obviously, the ball took a lot of damage over the course of a game, and by the end it was extremely difficult for batters to see, much less hit hard.
The height of the Dead Ball Era was 1905, when the major-league batting average was .249, and only three American Leaguers hit over .300. Elmer Flick won the batting title with a .308 average, higher only than Carl Yastrzemski‘s .301 title in 1968. Every AL pitching staff had an ERA under 3.00, and Christy Mathewson won the NL ERA title with a 1.28.
As a result of tighter stitching on the balls, 1920 marked the beginning of the end for this pitchers’ paradise. Trick pitches, like the spitball, were also outlawed. After Cleveland shortstop Ray Chapman was tragically killed by a pitch on August 16, 1920, the rules committee decided that only clean (and therefore easily seen) balls could be used. The unscuffed balls resulted in higher batting averages, and the tighter stitching made those hits go farther, resulting in a home run explosion. The new era of offense began with a bang, as Babe Ruth batted .376 and smashed an unheard-of 54 homers. His .847 slugging percentage that season is still the standard.