In baseball, the umpire—often called "blue" for their uniform—is the official who enforces the rules, makes judgment calls, and manages disputes, similar to a referee in other sports. While early games featured a single official, since the turn of the 20th century, umpires work in rotating crews, with the home plate umpire (umpire-in-chief) calling balls and strikes while wearing catcher-like protective gear, and field umpires stationed at the bases making calls on runners. The crew chief is typically the most experienced member, and crews rotate positions each game, though Hall of Famer Bill Klem famously spent his first 16 years exclusively behind the plate. For major events like the MLB All-Star Game and playoffs, leagues expand to six umpires, adding left- and right-field specialists to cover outfield plays. This structured system ensures accurate calls and player safety, highlighting the umpire's crucial role in maintaining the integrity of the game.