Baseball in the United States

Major League Baseball (MLB) is the highest level of baseball in the United States. The sport is one of the most popular sports in the U.S. for both participants and spectators. The World Series of MLB is the culmination of baseball's postseason each October. It is played between the winner of each of the two leagues, the American League and the National League, and the winner is determined through a best-of-seven playoff.

As baseball developed over 150 years ago in the Northeastern United States, it has been played and followed in the region longer than any other region in the nation. As of 2022, the Philadelphia Phillies, founded in 1883, are the oldest continuous same-name, same-city franchise in both Major League Baseball and all of American professional sports.

An extensive minor league baseball system covers most mid-sized cities in the United States. Minor league baseball teams are organized in a six-tier hierarchy, in which the highest teams (AAA) are in major cities that do not have a major league team but often have a major team in another sport, and each level occupies progressively smaller cities. The lowest levels of professional baseball serve primarily as development systems for the sport's most inexperienced prospects, with the absolute bottom, the rookie leagues, occupying the major league squads' spring training complexes and making no effort to earn money on their own.

Then, every four years in March, the World Baseball Classic is held, which is the national team game, the most popular baseball national team game. The Team USA won its first championship in 2017 and lost to Japan in 2023 to win the second place.

Some limited independent professional baseball exists, the most prominent being the Atlantic League, which occupies mostly suburban locales that are not eligible for high level minor league teams of their own. Outside the minor leagues are collegiate summer baseball leagues, which occupy towns even smaller than those at the lower end of minor league baseball and typically cannot support professional sports. Summer baseball is an amateur exercise and uses players that choose not to play for payment in order to remain eligible to play college baseball for their respective universities in the spring. At the absolute lowest end of the organized baseball system is senior amateur baseball (also known as Town Team Baseball), which typically plays its games only on weekends.