Legends tell the story of Abner Doubleday inventing the game of baseball in 1839. However, close inspection of the actual timeline of the sport and Doubleday's life make it clear that this tale has some inconsistencies. The modern game of baseball seems to have originated from two English games. Rounders and cricket had made their appearance in America, and people were likely playing them around the time of the Revolutionary War. In 1845, the New York Knickerbocker Baseball Club was founded. They needed guidelines for the game they were playing, and thus, standard rules were born.
Baseball involves play between two teams of nine players each. Each team strives to score more runs than the other. A standard baseball game involves nine innings in which the teams take turns playing offensively and defensively. Players take turns batting, during which the pitcher throws the baseball to the batter, who tries to hit it. The pitcher tries to get the batter to swing at unhittable balls to get the batter out. Meanwhile, the batter tries to hit the balls. If the batter connects with a pitch, the ball enters play into the field, where fielders work to get the ball to players assigned to bases. If a baseman gets the ball before a runner gets to the base, the baseman can tag the base and/or the runner to get the runner out. If a runner gets to a base before the ball, the runner will be safe and can remain there. Runners strive to run to each base and get back to home plate. Returning to home plate safely earns a run for the team.
As the years have unfolded, baseball has evolved significantly. Rules have been updated and added to the game, which has resulted in a number of significant changes to the sport. When baseball was first organized, the teams did not play the traditional nine innings. Instead, they played until they accomplished a set number of runs, which were called "counts" at this time. In the early days of baseball, the pitcher's job was very different. Instead of trying to strike out the batter, the pitcher tried to loft hittable balls across the plate for the batter to hit. Early baseball players played by the "first bounce rule." This rule stated that a batter would be out if a fielder caught a ball either on the fly or the first bounce. And base runners ran the bases while facing the potential for having fielders throw the ball directly at them to get them out.
The 20th century also saw a number of significant changes to the baseball rule book. In 1908, the sacrifice fly rule was added to the baseball rules. Baseball diamonds became regulation size, and all baseball parks had to comply with regulations. Rules were added to determine parameters of the strike zone. Most recently, Major League Baseball added limited use of instant replay to assist umpires with calls.