The history of baseball in the United States dates to the 19th century, when boys and amateur enthusiasts played a baseball-like game by their own informal rules using homemade equipment. The popularity of the sport grew and amateur men's ball clubs were formed in the 1830–50s. Semi-professional baseball clubs followed in the 1860s, and the first professional leagues arrived in the post-American Civil War 1870s.

Baseball is a bat-and-ball sport played between two teams of nine players each, taking turns batting and fielding. The game occurs over the course of several plays, with each play generally beginning when a player on the fielding team, called the pitcher, throws a ball that a player on the batting team, called the batter, tries to hit with a bat. The objective of the offensive team is to hit the ball into the field of play, away from the other team's players, allowing its players to run the bases, having them advance counter-clockwise around four bases to score what are called "runs". The objective of the defensive team is to prevent batters from becoming runners, and to prevent runners' advance around the bases. A run is scored when a runner legally advances around the bases in order and touches home plate.