Since the game evolved from several poorly documented sources over the course of hundreds of years, very little is known about the origin of baseball. Baseball's ancestors are believed to be English folk games such as stoolball, Tip-cat, cat and dog, and cricket, though the earliest know reference to game itself is a 1791 bylaw which forbade "base ball" within 80 yards of a meeting house in Pittsfield, Massachusetts.

The man who is credited with ushering in Baseball in its modern, recognizable form is Alexander Cartwright. Cartwright was a member of a club called the New York Knickerbockers, which played a stick-and-ball game called the "town game." In 1845 Cartwright and a committee he organized worked on converting the rules of the playground game into something elaborate and interesting enough to attract adults. Despite writing the "Knickerbocker Rules," as they were called, the first game played under them found Cartwright's team completely dominated by the "New York Nine" with a score of 23-1.

The "National Association of Professional Base Ball Players," which is often credited with being the first major league, existed from 1871 to 1875. The very same year it disbanded, the still extant "National League of Professional Base Ball Clubs" formed. Clubs now were able to contractually bind their players to playing with them, despite offers from higher paying clubs. In return, clubs were obligated to play their full schedule of games, rather than forfeiting games once there was no chance of winning the league championship. New leagues were formed regularly, but few had any staying power. The most successful was the American Association, whose champions met regularly with the champions of the National League post-season, an early form of the World Series. The American League, which today makes up the other half of major league baseball, formed in 1893, though it didn't start operating as a major league until 1901.

The era from 1901-1919 is known as the "dead ball era" in baseball. The name comes from the fact that cash strapped club owners would often make a single baseball last the entire game to keep their equipment budget low. By the end of the game, the ball would be stained with grass, mud, and tobacco juice, and the malleable ball would be misshapen and nearly unusable. The era came to end with a 1920 rule that dictated that umpires had to replace the baseball once it had become scuffed or discolored (in the modern professional game, baseballs have an average lifespan of merely six pitches). Around the same time, a player affectionately known as "Babe" Ruth was sold to the Yankees from the Red Sox. Ruth's unprecedented hitting power demonstrated a new way to play the game, one that proved it was feasible to win games through slugging alone. This shift in the game ushered in "sluggers" like Lou Gehrig, Jimmie Foxx, and Hank Greenberg who wowed crowds with their home run numbers and the sheer distance that they could swat the ball.

In 1947 Branch Rickley, the general manager of the Brooklyn Dodgers, signed Jackie Robinson and broke the color barrier which had haunted baseball for 50 years. Though there was no official ban on African American ballplayers, attempts in the past to sign players from the Negro Leagues were frustrated by league officials and rival teams. Rickley scouted players in secrecy, and finally chose Robinson not because he believed him to be the best player among the candidates, but rather because he had the strongest resolve of spirit to withstand the abuse he would have to face. Robinson's talent, however, proved formidable, as his skill on the field earned him the very first Rookie of the Year award. Robinson was quick on his feet an impressive sprinter, and his influence helped baserunning and fielding return to prominence in an era when power hitting was seen as the most valuable asset for a team.

Baseball continued to enjoy popularity until 1994, when a strike among players embittered many fans. The sport was in part invigorated by the home run race between Mark Maguire and Sammy Sosa in 1998. Both sluggers vied to achieve the most coveted record in baseball by defeating Roger Maris' 61 home runs in a single season. They both smashed the record, with Sosa completing the season with 66 home runs, just behind McGwire's incredible 70. However, even McGwire's record was soon beaten by Barry Bonds, who slugged an astronomical 73 homers during his 2001 season.