In baseball, the dead-ball era was the period from around 1900 to the emergence of Babe Ruth as a power hitter in 1919. That year, Ruth hit a then-league record 29 home runs, a spectacular feat at that time.
Teams played in spacious ball parks that limited hitting for power, and, compared to modern baseballs, the ball used then was "dead" both by design and from overuse. In addition ball scuffing and adulteration by pitchers was not against the rules during this period.
This era was characterized by low-scoring games and a lack of home runs. The lowest league run average in history was in 1908, when teams averaged only 3.4 runs per game.
During the dead-ball era, baseball was much more of a strategy-driven game, using a style of play now known as small ball or inside baseball. It relied much more on plays such as the stolen bases and hit-and-run than on home runs. These strategies emphasized speed, perhaps by necessity.
Low-power hits like the Baltimore Chop, developed in the 1890s by the Baltimore Orioles, were used to get on base. Once on base, a runner would often steal or be bunted over to second base and move to third base or score on a hit-and-run play. In no other era have teams stolen as many bases as in the dead-ball era.
On 13 occasions between 1900 and 1920, the league leader in home runs had fewer than 10 home runs for the season; on four occasions the league leaders had 20 or more home runs. Meanwhile, there were 20 instances where the league leader in triples had 20 or more.
Despite their speed, teams struggled to score during the dead-ball era. Major league cumulative batting averages ranged between .239 and .279 in the National League and between .239 and .283 in the American League. The lack of power in the game also meant lower slugging averages and on-base percentages, as pitchers could challenge hitters more without the threat of the home run. The nadir of the dead-ball era was around 1907 and 1908, with a league-wide batting average of .239, slugging average of .306, and ERA under 2.40. In the latter year, the Chicago White Sox hit three home runs for the entire season, yet they finished 88-64, just a couple of games from winning the pennant.
--White Sox manager Fielder Jones, after his 1906 "Hitless Wonders" won the World Series with a .230 club batting average
Some players and fans complained about the low-scoring games, and baseball sought to remedy the situation. In 1909, Ben Shibe invented the cork-centered ball, which the Reach Company--official ball supplier to the American League (AL)--began marketing.Spalding, who supplied the National League (NL), followed with its own cork-center ball.
The change in the ball dramatically affected play in both leagues. In 1910, the American League batting average was .243; in 1911, it rose to .273. The National League saw a jump in the league batting average from .256 in 1910 to .272 in 1912. The 1911 season happened to be the best of Ty Cobb's career; he batted .420 with 248 hits. Joe Jackson hit .408 in 1911, and the next year Cobb batted .410. These were the only .400 averages between 1902 and 1919.
In 1913, however, minor league pitcher Russ Ford noticed that a ball scuffed against a concrete wall quickly dived as it reached the batter. This so-called emery pitch, together with the spitball, gave pitchers greatly increased control of the batter, especially since a single ball – rarely replaced during a game – would become increasingly scuffed as play progressed, as well as more difficult to see as it became dirtier. By 1914 run scoring was essentially back to the pre-1911 years and remained so until 1919.
In this era, Frank Baker earned the nickname "Home Run" Baker merely for hitting two home runs in the 1911 World Series; although he led the American League in home runs four times (1911-1914), his highest home run season was 1913, when he hit 12 home runs, and he finished with 96 home runs for his career. The best homerun hitter of the dead-ball era was Philadelphia Phillies outfielder "Cactus" Gavvy Cravath. He led the National League in home runs six times, with a high total of 24 for the pennant-winning Phillies in 1915 and seasons of 19 home runs each in 1913 and 1914. However, Cravath played in the Baker Bowl, a notoriously hitter-friendly park with only a short 280-foot (85 m) distance from the plate to the right field wall.
The following factors contributed to the dramatic decline in runs scored during the dead-ball era:
The foul strike rule was a major rule change that, in just a few years, sent baseball from a high-scoring game to a game where scoring any runs was a struggle. Under the foul strike rule, a batter who fouls off is charged with a strike unless he already has two strikes against him. The National League adopted the foul strike rule in 1901 and the American League followed suit in 1903. Prior to this rule, foul balls did not count as strikes. Thus, a batter could foul off a countless number of pitches with no strikes counted against him--except for bunt attempts. This gave batters an enormous advantage before the foul strike rule removed it. 
Before 1921, it was common for a baseball to be in play for over 100 pitches. Players used the same ball until it started to unravel. Early baseball leagues were very cost-conscious, so fans had to throw back balls that had been hit into the stands. The longer the ball was in play, the softer it became--and hitting a heavily used, softer ball for distance is much more difficult than hitting a new, harder one. The ball was also softer to begin with, making home runs less likely.
The ball was also hard to hit because pitchers could manipulate it before a pitch. For example, the spitball pitch was permitted in baseball until 1921. Pitchers often marked the ball, scuffed it, spat on it--anything they could to influence the ball's motion. This made the ball "dance" and curve much more than it does now, making it more difficult to hit. Tobacco juice was often added to the ball as well, which discolored it. This made the ball difficult to see, especially since baseball parks did not have lights until the late 1930s. This made both hitting and fielding more difficult.
Many ballparks were large by modern standards, such as the West Side Grounds of the Chicago Cubs, which was 560 feet (170 m) to the center field fence, and the Huntington Avenue Grounds of the Boston Red Sox, which was 635 feet (194 m) to the center field fence. The dimensions of Braves Field prompted Ty Cobb to say that no one would ever hit the ball out of it.
The dead-ball era ended suddenly. By 1921, offenses were scoring 40% more runs and hitting four times as many home runs as they had in 1918. Baseball historians debate the abruptness of this change, with no consensus on its cause. Six popular theories have been advanced: